diff --git a/.DS_Store b/.DS_Store deleted file mode 100644 index 4732423..0000000 Binary files a/.DS_Store and /dev/null differ diff --git a/sqlite3/README.md b/sqlite3/README.md deleted file mode 100644 index 7fc1e51..0000000 --- a/sqlite3/README.md +++ /dev/null @@ -1,4 +0,0 @@ -sqlite3_examples -================ - -Syntax examples for working with SQLite databases via the sqlite3 module in Python diff --git a/sqlite3/create_db.py b/sqlite3/create_db.py deleted file mode 100644 index 7099675..0000000 --- a/sqlite3/create_db.py +++ /dev/null @@ -1,30 +0,0 @@ -# 10/28/2013 Sebastian Raschka -# Syntax basics for creating sqlite3 data bases - -import sqlite3 - -# create new db and make connection -conn = sqlite3.connect('zinc_db1.db') -c = conn.cursor() - -# create table -c.execute('''CREATE TABLE zinc_db1 - (zinc_id PRIMARY KEY, purchasable TEXT, non_rot_bonds INT)''') - -# Insert one row of data -c.execute("INSERT INTO zinc_db1 VALUES ('ZINC00895032','YES', 4)") - -# Insert multiple lines of data -multi_lines =[ ('ZINC00895033','YES', 1), - ('ZINC00895034','NO', 0), - ('ZINC00895035','YES', 3), - ('ZINC00895036','YES', 9), - ('ZINC00895037','YES', 10) - ] -c.executemany('INSERT INTO zinc_db1 VALUES (?,?,?)', multi_lines) - -# Save (commit) the changes -conn.commit() - -# close connection -conn.close() diff --git a/sqlite3/query_db.py b/sqlite3/query_db.py deleted file mode 100644 index 40bd2d7..0000000 --- a/sqlite3/query_db.py +++ /dev/null @@ -1,28 +0,0 @@ -# 10/28/2013 Sebastian Raschka -# Syntax basics for querying sqlite3 data bases - -import sqlite3 - -# open existing database -conn = sqlite3.connect('zinc_db1.db') -c = conn.cursor() - -# print all lines ordered by number of non_rot_bonds -for row in c.execute('SELECT * FROM zinc_db1 ORDER BY non_rot_bonds'): - print row - -# print all lines that are purchasable and have <= 7 rotatable bonds -t = ('YES',7,) -for row in c.execute('SELECT * FROM zinc_db1 WHERE purchasable=? AND non_rot_bonds <= ?', t): - print row - -# print all lines that are purchasable and have <= 7 rotatable bonds -t = ('YES',7,) -c.execute('SELECT * FROM zinc_db1 WHERE purchasable=? AND non_rot_bonds <= ?', t) -rows = c.fetchall() -for r in rows: - print r - -# close connection -conn.close() - diff --git a/sqlite3/update_db.py b/sqlite3/update_db.py deleted file mode 100644 index 50c4a63..0000000 --- a/sqlite3/update_db.py +++ /dev/null @@ -1,46 +0,0 @@ -# 10/28/2013 Sebastian Raschka -# Syntax basics for updating sqlite3 data bases - -import sqlite3 - -# make connection to existing db -conn = sqlite3.connect('zinc_db1.db') -c = conn.cursor() - -# update field (no insert if id doesn't exist) -t = ('NO', 'ZINC00895033', ) -c.execute("UPDATE zinc_db1 SET purchasable=? WHERE zinc_id=?", t) -print "Total number of rows changed:", conn.total_changes - - -# update, or insert when id does not exist -# here: updates rotatable bonds if record with primary key zinc_id exists,
-# else inserts new record an sets purchasable to 0 -c.execute("""INSERT OR REPLACE INTO zinc_db1 (zinc_id, rotatable_bonds, purchasable) - VALUES ( 'ZINC123456798', - 3, - COALESCE((SELECT purchasable from zinc_db1 WHERE zinc_id = 'ZINC123456798'), 0) - )""") - - - -# delete rows -t = ('NO', ) -c.execute("DELETE FROM zinc_db1 WHERE purchasable=?", t) -print "Total number of rows deleted: ", conn.total_changes - -# add column -c.execute("ALTER TABLE zinc_db1 ADD COLUMN 'keto_oxy' TEXT") - -# save changes -conn.commit() - -# print column names -c.execute("SELECT * FROM zinc_db1") -col_name_list = [tup[0] for tup in c.description] -print col_name_list - - - -# close connection -conn.close() diff --git a/sqlite3_howto/Images/1_sqlite3_init_db.png b/sqlite3_howto/Images/1_sqlite3_init_db.png new file mode 100644 index 0000000..c85f420 Binary files /dev/null and b/sqlite3_howto/Images/1_sqlite3_init_db.png differ diff --git a/sqlite3_howto/Images/2_sqlite3_add_col.png b/sqlite3_howto/Images/2_sqlite3_add_col.png new file mode 100644 index 0000000..63e1c50 Binary files /dev/null and b/sqlite3_howto/Images/2_sqlite3_add_col.png differ diff --git a/sqlite3_howto/Images/3_sqlite3_insert_update.png b/sqlite3_howto/Images/3_sqlite3_insert_update.png new file mode 100644 index 0000000..9cb1b26 Binary files /dev/null and b/sqlite3_howto/Images/3_sqlite3_insert_update.png differ diff --git a/sqlite3_howto/Images/4_sqlite3_unique_index.png b/sqlite3_howto/Images/4_sqlite3_unique_index.png new file mode 100644 index 0000000..a3ad45a Binary files /dev/null and b/sqlite3_howto/Images/4_sqlite3_unique_index.png differ diff --git a/sqlite3_howto/Images/5_sqlite3_date_time.png b/sqlite3_howto/Images/5_sqlite3_date_time.png new file mode 100644 index 0000000..b28a115 Binary files /dev/null and b/sqlite3_howto/Images/5_sqlite3_date_time.png differ diff --git a/sqlite3_howto/Images/5_sqlite3_date_time_2.png b/sqlite3_howto/Images/5_sqlite3_date_time_2.png new file mode 100644 index 0000000..c077481 Binary files /dev/null and b/sqlite3_howto/Images/5_sqlite3_date_time_2.png differ diff --git a/sqlite3_howto/Images/6_sqlite3_print_selecting_rows.png b/sqlite3_howto/Images/6_sqlite3_print_selecting_rows.png new file mode 100644 index 0000000..26be818 Binary files /dev/null and b/sqlite3_howto/Images/6_sqlite3_print_selecting_rows.png differ diff --git a/sqlite3_howto/Images/7_sqlite3_get_colnames_1.png b/sqlite3_howto/Images/7_sqlite3_get_colnames_1.png new file mode 100644 index 0000000..a400cd4 Binary files /dev/null and b/sqlite3_howto/Images/7_sqlite3_get_colnames_1.png differ diff --git a/sqlite3_howto/Images/7_sqlite3_get_colnames_2.png b/sqlite3_howto/Images/7_sqlite3_get_colnames_2.png new file mode 100644 index 0000000..8b3d95f Binary files /dev/null and b/sqlite3_howto/Images/7_sqlite3_get_colnames_2.png differ diff --git a/sqlite3_howto/Images/8_sqlite3_print_db_info_1.png b/sqlite3_howto/Images/8_sqlite3_print_db_info_1.png new file mode 100644 index 0000000..a400cd4 Binary files /dev/null and b/sqlite3_howto/Images/8_sqlite3_print_db_info_1.png differ diff --git a/sqlite3_howto/Images/8_sqlite3_print_db_info_2.png b/sqlite3_howto/Images/8_sqlite3_print_db_info_2.png new file mode 100644 index 0000000..9aac8e6 Binary files /dev/null and b/sqlite3_howto/Images/8_sqlite3_print_db_info_2.png differ diff --git a/sqlite3_howto/Images/sqlite_python_logo.png b/sqlite3_howto/Images/sqlite_python_logo.png new file mode 100644 index 0000000..25740d3 Binary files /dev/null and b/sqlite3_howto/Images/sqlite_python_logo.png differ diff --git a/sqlite3_howto/LICENSE b/sqlite3_howto/LICENSE new file mode 100644 index 0000000..ef7e7ef --- /dev/null +++ b/sqlite3_howto/LICENSE @@ -0,0 +1,674 @@ +GNU GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The GNU General Public License is a free, copyleft license for +software and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. By contrast, +the GNU General Public License is intended to guarantee your freedom to +share and change all versions of a program--to make sure it remains free +software for all its users. We, the Free Software Foundation, use the +GNU General Public License for most of our software; it applies also to +any other work released this way by its authors. You can apply it to +your programs, too. + + When we speak of free software, we are referring to freedom, not +price. Our General Public Licenses are designed to make sure that you +have the freedom to distribute copies of free software (and charge for +them if you wish), that you receive source code or can get it if you +want it, that you can change the software or use pieces of it in new +free programs, and that you know you can do these things. + + To protect your rights, we need to prevent others from denying you +these rights or asking you to surrender the rights. Therefore, you have +certain responsibilities if you distribute copies of the software, or if +you modify it: responsibilities to respect the freedom of others. + + For example, if you distribute copies of such a program, whether +gratis or for a fee, you must pass on to the recipients the same +freedoms that you received. You must make sure that they, too, receive +or can get the source code. And you must show them these terms so they +know their rights. + + Developers that use the GNU GPL protect your rights with two steps: +(1) assert copyright on the software, and (2) offer you this License +giving you legal permission to copy, distribute and/or modify it. + + For the developers' and authors' protection, the GPL clearly explains +that there is no warranty for this free software. For both users' and +authors' sake, the GPL requires that modified versions be marked as +changed, so that their problems will not be attributed erroneously to +authors of previous versions. + + Some devices are designed to deny users access to install or run +modified versions of the software inside them, although the manufacturer +can do so. This is fundamentally incompatible with the aim of +protecting users' freedom to change the software. The systematic +pattern of such abuse occurs in the area of products for individuals to +use, which is precisely where it is most unacceptable. Therefore, we +have designed this version of the GPL to prohibit the practice for those +products. If such problems arise substantially in other domains, we +stand ready to extend this provision to those domains in future versions +of the GPL, as needed to protect the freedom of users. + + Finally, every program is threatened constantly by software patents. +States should not allow patents to restrict development and use of +software on general-purpose computers, but in those that do, we wish to +avoid the special danger that patents applied to a free program could +make it effectively proprietary. To prevent this, the GPL assures that +patents cannot be used to render the program non-free. + + The precise terms and conditions for copying, distribution and +modification follow. + + TERMS AND CONDITIONS + + 0. Definitions. + + "This License" refers to version 3 of the GNU General Public License. + + "Copyright" also means copyright-like laws that apply to other kinds of +works, such as semiconductor masks. + + "The Program" refers to any copyrightable work licensed under this +License. Each licensee is addressed as "you". "Licensees" and +"recipients" may be individuals or organizations. + + To "modify" a work means to copy from or adapt all or part of the work +in a fashion requiring copyright permission, other than the making of an +exact copy. The resulting work is called a "modified version" of the +earlier work or a work "based on" the earlier work. + + A "covered work" means either the unmodified Program or a work based +on the Program. + + To "propagate" a work means to do anything with it that, without +permission, would make you directly or secondarily liable for +infringement under applicable copyright law, except executing it on a +computer or modifying a private copy. Propagation includes copying, +distribution (with or without modification), making available to the +public, and in some countries other activities as well. + + To "convey" a work means any kind of propagation that enables other +parties to make or receive copies. Mere interaction with a user through +a computer network, with no transfer of a copy, is not conveying. + + An interactive user interface displays "Appropriate Legal Notices" +to the extent that it includes a convenient and prominently visible +feature that (1) displays an appropriate copyright notice, and (2) +tells the user that there is no warranty for the work (except to the +extent that warranties are provided), that licensees may convey the +work under this License, and how to view a copy of this License. If +the interface presents a list of user commands or options, such as a +menu, a prominent item in the list meets this criterion. + + 1. Source Code. + + The "source code" for a work means the preferred form of the work +for making modifications to it. "Object code" means any non-source +form of a work. + + A "Standard Interface" means an interface that either is an official +standard defined by a recognized standards body, or, in the case of +interfaces specified for a particular programming language, one that +is widely used among developers working in that language. + + The "System Libraries" of an executable work include anything, other +than the work as a whole, that (a) is included in the normal form of +packaging a Major Component, but which is not part of that Major +Component, and (b) serves only to enable use of the work with that +Major Component, or to implement a Standard Interface for which an +implementation is available to the public in source code form. A +"Major Component", in this context, means a major essential component +(kernel, window system, and so on) of the specific operating system +(if any) on which the executable work runs, or a compiler used to +produce the work, or an object code interpreter used to run it. + + The "Corresponding Source" for a work in object code form means all +the source code needed to generate, install, and (for an executable +work) run the object code and to modify the work, including scripts to +control those activities. However, it does not include the work's +System Libraries, or general-purpose tools or generally available free +programs which are used unmodified in performing those activities but +which are not part of the work. For example, Corresponding Source +includes interface definition files associated with source files for +the work, and the source code for shared libraries and dynamically +linked subprograms that the work is specifically designed to require, +such as by intimate data communication or control flow between those +subprograms and other parts of the work. + + The Corresponding Source need not include anything that users +can regenerate automatically from other parts of the Corresponding +Source. + + The Corresponding Source for a work in source code form is that +same work. + + 2. Basic Permissions. + + All rights granted under this License are granted for the term of +copyright on the Program, and are irrevocable provided the stated +conditions are met. This License explicitly affirms your unlimited +permission to run the unmodified Program. The output from running a +covered work is covered by this License only if the output, given its +content, constitutes a covered work. This License acknowledges your +rights of fair use or other equivalent, as provided by copyright law. + + You may make, run and propagate covered works that you do not +convey, without conditions so long as your license otherwise remains +in force. You may convey covered works to others for the sole purpose +of having them make modifications exclusively for you, or provide you +with facilities for running those works, provided that you comply with +the terms of this License in conveying all material for which you do +not control copyright. Those thus making or running the covered works +for you must do so exclusively on your behalf, under your direction +and control, on terms that prohibit them from making any copies of +your copyrighted material outside their relationship with you. + + Conveying under any other circumstances is permitted solely under +the conditions stated below. Sublicensing is not allowed; section 10 +makes it unnecessary. + + 3. Protecting Users' Legal Rights From Anti-Circumvention Law. + + No covered work shall be deemed part of an effective technological +measure under any applicable law fulfilling obligations under article +11 of the WIPO copyright treaty adopted on 20 December 1996, or +similar laws prohibiting or restricting circumvention of such +measures. + + When you convey a covered work, you waive any legal power to forbid +circumvention of technological measures to the extent such circumvention +is effected by exercising rights under this License with respect to +the covered work, and you disclaim any intention to limit operation or +modification of the work as a means of enforcing, against the work's +users, your or third parties' legal rights to forbid circumvention of +technological measures. + + 4. Conveying Verbatim Copies. + + You may convey verbatim copies of the Program's source code as you +receive it, in any medium, provided that you conspicuously and +appropriately publish on each copy an appropriate copyright notice; +keep intact all notices stating that this License and any +non-permissive terms added in accord with section 7 apply to the code; +keep intact all notices of the absence of any warranty; and give all +recipients a copy of this License along with the Program. + + You may charge any price or no price for each copy that you convey, +and you may offer support or warranty protection for a fee. + + 5. Conveying Modified Source Versions. + + You may convey a work based on the Program, or the modifications to +produce it from the Program, in the form of source code under the +terms of section 4, provided that you also meet all of these conditions: + + a) The work must carry prominent notices stating that you modified + it, and giving a relevant date. + + b) The work must carry prominent notices stating that it is + released under this License and any conditions added under section + 7. This requirement modifies the requirement in section 4 to + "keep intact all notices". + + c) You must license the entire work, as a whole, under this + License to anyone who comes into possession of a copy. This + License will therefore apply, along with any applicable section 7 + additional terms, to the whole of the work, and all its parts, + regardless of how they are packaged. This License gives no + permission to license the work in any other way, but it does not + invalidate such permission if you have separately received it. + + d) If the work has interactive user interfaces, each must display + Appropriate Legal Notices; however, if the Program has interactive + interfaces that do not display Appropriate Legal Notices, your + work need not make them do so. + + A compilation of a covered work with other separate and independent +works, which are not by their nature extensions of the covered work, +and which are not combined with it such as to form a larger program, +in or on a volume of a storage or distribution medium, is called an +"aggregate" if the compilation and its resulting copyright are not +used to limit the access or legal rights of the compilation's users +beyond what the individual works permit. Inclusion of a covered work +in an aggregate does not cause this License to apply to the other +parts of the aggregate. + + 6. Conveying Non-Source Forms. + + You may convey a covered work in object code form under the terms +of sections 4 and 5, provided that you also convey the +machine-readable Corresponding Source under the terms of this License, +in one of these ways: + + a) Convey the object code in, or embodied in, a physical product + (including a physical distribution medium), accompanied by the + Corresponding Source fixed on a durable physical medium + customarily used for software interchange. + + b) Convey the object code in, or embodied in, a physical product + (including a physical distribution medium), accompanied by a + written offer, valid for at least three years and valid for as + long as you offer spare parts or customer support for that product + model, to give anyone who possesses the object code either (1) a + copy of the Corresponding Source for all the software in the + product that is covered by this License, on a durable physical + medium customarily used for software interchange, for a price no + more than your reasonable cost of physically performing this + conveying of source, or (2) access to copy the + Corresponding Source from a network server at no charge. + + c) Convey individual copies of the object code with a copy of the + written offer to provide the Corresponding Source. This + alternative is allowed only occasionally and noncommercially, and + only if you received the object code with such an offer, in accord + with subsection 6b. + + d) Convey the object code by offering access from a designated + place (gratis or for a charge), and offer equivalent access to the + Corresponding Source in the same way through the same place at no + further charge. You need not require recipients to copy the + Corresponding Source along with the object code. If the place to + copy the object code is a network server, the Corresponding Source + may be on a different server (operated by you or a third party) + that supports equivalent copying facilities, provided you maintain + clear directions next to the object code saying where to find the + Corresponding Source. Regardless of what server hosts the + Corresponding Source, you remain obligated to ensure that it is + available for as long as needed to satisfy these requirements. + + e) Convey the object code using peer-to-peer transmission, provided + you inform other peers where the object code and Corresponding + Source of the work are being offered to the general public at no + charge under subsection 6d. + + A separable portion of the object code, whose source code is excluded +from the Corresponding Source as a System Library, need not be +included in conveying the object code work. + + A "User Product" is either (1) a "consumer product", which means any +tangible personal property which is normally used for personal, family, +or household purposes, or (2) anything designed or sold for incorporation +into a dwelling. In determining whether a product is a consumer product, +doubtful cases shall be resolved in favor of coverage. For a particular +product received by a particular user, "normally used" refers to a +typical or common use of that class of product, regardless of the status +of the particular user or of the way in which the particular user +actually uses, or expects or is expected to use, the product. A product +is a consumer product regardless of whether the product has substantial +commercial, industrial or non-consumer uses, unless such uses represent +the only significant mode of use of the product. + + "Installation Information" for a User Product means any methods, +procedures, authorization keys, or other information required to install +and execute modified versions of a covered work in that User Product from +a modified version of its Corresponding Source. The information must +suffice to ensure that the continued functioning of the modified object +code is in no case prevented or interfered with solely because +modification has been made. + + If you convey an object code work under this section in, or with, or +specifically for use in, a User Product, and the conveying occurs as +part of a transaction in which the right of possession and use of the +User Product is transferred to the recipient in perpetuity or for a +fixed term (regardless of how the transaction is characterized), the +Corresponding Source conveyed under this section must be accompanied +by the Installation Information. But this requirement does not apply +if neither you nor any third party retains the ability to install +modified object code on the User Product (for example, the work has +been installed in ROM). + + The requirement to provide Installation Information does not include a +requirement to continue to provide support service, warranty, or updates +for a work that has been modified or installed by the recipient, or for +the User Product in which it has been modified or installed. Access to a +network may be denied when the modification itself materially and +adversely affects the operation of the network or violates the rules and +protocols for communication across the network. + + Corresponding Source conveyed, and Installation Information provided, +in accord with this section must be in a format that is publicly +documented (and with an implementation available to the public in +source code form), and must require no special password or key for +unpacking, reading or copying. + + 7. Additional Terms. + + "Additional permissions" are terms that supplement the terms of this +License by making exceptions from one or more of its conditions. +Additional permissions that are applicable to the entire Program shall +be treated as though they were included in this License, to the extent +that they are valid under applicable law. If additional permissions +apply only to part of the Program, that part may be used separately +under those permissions, but the entire Program remains governed by +this License without regard to the additional permissions. + + When you convey a copy of a covered work, you may at your option +remove any additional permissions from that copy, or from any part of +it. (Additional permissions may be written to require their own +removal in certain cases when you modify the work.) You may place +additional permissions on material, added by you to a covered work, +for which you have or can give appropriate copyright permission. + + Notwithstanding any other provision of this License, for material you +add to a covered work, you may (if authorized by the copyright holders of +that material) supplement the terms of this License with terms: + + a) Disclaiming warranty or limiting liability differently from the + terms of sections 15 and 16 of this License; or + + b) Requiring preservation of specified reasonable legal notices or + author attributions in that material or in the Appropriate Legal + Notices displayed by works containing it; or + + c) Prohibiting misrepresentation of the origin of that material, or + requiring that modified versions of such material be marked in + reasonable ways as different from the original version; or + + d) Limiting the use for publicity purposes of names of licensors or + authors of the material; or + + e) Declining to grant rights under trademark law for use of some + trade names, trademarks, or service marks; or + + f) Requiring indemnification of licensors and authors of that + material by anyone who conveys the material (or modified versions of + it) with contractual assumptions of liability to the recipient, for + any liability that these contractual assumptions directly impose on + those licensors and authors. + + All other non-permissive additional terms are considered "further +restrictions" within the meaning of section 10. If the Program as you +received it, or any part of it, contains a notice stating that it is +governed by this License along with a term that is a further +restriction, you may remove that term. If a license document contains +a further restriction but permits relicensing or conveying under this +License, you may add to a covered work material governed by the terms +of that license document, provided that the further restriction does +not survive such relicensing or conveying. + + If you add terms to a covered work in accord with this section, you +must place, in the relevant source files, a statement of the +additional terms that apply to those files, or a notice indicating +where to find the applicable terms. + + Additional terms, permissive or non-permissive, may be stated in the +form of a separately written license, or stated as exceptions; +the above requirements apply either way. + + 8. Termination. + + You may not propagate or modify a covered work except as expressly +provided under this License. Any attempt otherwise to propagate or +modify it is void, and will automatically terminate your rights under +this License (including any patent licenses granted under the third +paragraph of section 11). + + However, if you cease all violation of this License, then your +license from a particular copyright holder is reinstated (a) +provisionally, unless and until the copyright holder explicitly and +finally terminates your license, and (b) permanently, if the copyright +holder fails to notify you of the violation by some reasonable means +prior to 60 days after the cessation. + + Moreover, your license from a particular copyright holder is +reinstated permanently if the copyright holder notifies you of the +violation by some reasonable means, this is the first time you have +received notice of violation of this License (for any work) from that +copyright holder, and you cure the violation prior to 30 days after +your receipt of the notice. + + Termination of your rights under this section does not terminate the +licenses of parties who have received copies or rights from you under +this License. If your rights have been terminated and not permanently +reinstated, you do not qualify to receive new licenses for the same +material under section 10. + + 9. Acceptance Not Required for Having Copies. + + You are not required to accept this License in order to receive or +run a copy of the Program. Ancillary propagation of a covered work +occurring solely as a consequence of using peer-to-peer transmission +to receive a copy likewise does not require acceptance. However, +nothing other than this License grants you permission to propagate or +modify any covered work. These actions infringe copyright if you do +not accept this License. Therefore, by modifying or propagating a +covered work, you indicate your acceptance of this License to do so. + + 10. Automatic Licensing of Downstream Recipients. + + Each time you convey a covered work, the recipient automatically +receives a license from the original licensors, to run, modify and +propagate that work, subject to this License. You are not responsible +for enforcing compliance by third parties with this License. + + An "entity transaction" is a transaction transferring control of an +organization, or substantially all assets of one, or subdividing an +organization, or merging organizations. If propagation of a covered +work results from an entity transaction, each party to that +transaction who receives a copy of the work also receives whatever +licenses to the work the party's predecessor in interest had or could +give under the previous paragraph, plus a right to possession of the +Corresponding Source of the work from the predecessor in interest, if +the predecessor has it or can get it with reasonable efforts. + + You may not impose any further restrictions on the exercise of the +rights granted or affirmed under this License. For example, you may +not impose a license fee, royalty, or other charge for exercise of +rights granted under this License, and you may not initiate litigation +(including a cross-claim or counterclaim in a lawsuit) alleging that +any patent claim is infringed by making, using, selling, offering for +sale, or importing the Program or any portion of it. + + 11. Patents. + + A "contributor" is a copyright holder who authorizes use under this +License of the Program or a work on which the Program is based. The +work thus licensed is called the contributor's "contributor version". + + A contributor's "essential patent claims" are all patent claims +owned or controlled by the contributor, whether already acquired or +hereafter acquired, that would be infringed by some manner, permitted +by this License, of making, using, or selling its contributor version, +but do not include claims that would be infringed only as a +consequence of further modification of the contributor version. For +purposes of this definition, "control" includes the right to grant +patent sublicenses in a manner consistent with the requirements of +this License. + + Each contributor grants you a non-exclusive, worldwide, royalty-free +patent license under the contributor's essential patent claims, to +make, use, sell, offer for sale, import and otherwise run, modify and +propagate the contents of its contributor version. + + In the following three paragraphs, a "patent license" is any express +agreement or commitment, however denominated, not to enforce a patent +(such as an express permission to practice a patent or covenant not to +sue for patent infringement). To "grant" such a patent license to a +party means to make such an agreement or commitment not to enforce a +patent against the party. + + If you convey a covered work, knowingly relying on a patent license, +and the Corresponding Source of the work is not available for anyone +to copy, free of charge and under the terms of this License, through a +publicly available network server or other readily accessible means, +then you must either (1) cause the Corresponding Source to be so +available, or (2) arrange to deprive yourself of the benefit of the +patent license for this particular work, or (3) arrange, in a manner +consistent with the requirements of this License, to extend the patent +license to downstream recipients. "Knowingly relying" means you have +actual knowledge that, but for the patent license, your conveying the +covered work in a country, or your recipient's use of the covered work +in a country, would infringe one or more identifiable patents in that +country that you have reason to believe are valid. + + If, pursuant to or in connection with a single transaction or +arrangement, you convey, or propagate by procuring conveyance of, a +covered work, and grant a patent license to some of the parties +receiving the covered work authorizing them to use, propagate, modify +or convey a specific copy of the covered work, then the patent license +you grant is automatically extended to all recipients of the covered +work and works based on it. + + A patent license is "discriminatory" if it does not include within +the scope of its coverage, prohibits the exercise of, or is +conditioned on the non-exercise of one or more of the rights that are +specifically granted under this License. You may not convey a covered +work if you are a party to an arrangement with a third party that is +in the business of distributing software, under which you make payment +to the third party based on the extent of your activity of conveying +the work, and under which the third party grants, to any of the +parties who would receive the covered work from you, a discriminatory +patent license (a) in connection with copies of the covered work +conveyed by you (or copies made from those copies), or (b) primarily +for and in connection with specific products or compilations that +contain the covered work, unless you entered into that arrangement, +or that patent license was granted, prior to 28 March 2007. + + Nothing in this License shall be construed as excluding or limiting +any implied license or other defenses to infringement that may +otherwise be available to you under applicable patent law. + + 12. No Surrender of Others' Freedom. + + If conditions are imposed on you (whether by court order, agreement or +otherwise) that contradict the conditions of this License, they do not +excuse you from the conditions of this License. If you cannot convey a +covered work so as to satisfy simultaneously your obligations under this +License and any other pertinent obligations, then as a consequence you may +not convey it at all. For example, if you agree to terms that obligate you +to collect a royalty for further conveying from those to whom you convey +the Program, the only way you could satisfy both those terms and this +License would be to refrain entirely from conveying the Program. + + 13. Use with the GNU Affero General Public License. + + Notwithstanding any other provision of this License, you have +permission to link or combine any covered work with a work licensed +under version 3 of the GNU Affero General Public License into a single +combined work, and to convey the resulting work. The terms of this +License will continue to apply to the part which is the covered work, +but the special requirements of the GNU Affero General Public License, +section 13, concerning interaction through a network will apply to the +combination as such. + + 14. Revised Versions of this License. + + The Free Software Foundation may publish revised and/or new versions of +the GNU General Public License from time to time. Such new versions will +be similar in spirit to the present version, but may differ in detail to +address new problems or concerns. + + Each version is given a distinguishing version number. If the +Program specifies that a certain numbered version of the GNU General +Public License "or any later version" applies to it, you have the +option of following the terms and conditions either of that numbered +version or of any later version published by the Free Software +Foundation. If the Program does not specify a version number of the +GNU General Public License, you may choose any version ever published +by the Free Software Foundation. + + If the Program specifies that a proxy can decide which future +versions of the GNU General Public License can be used, that proxy's +public statement of acceptance of a version permanently authorizes you +to choose that version for the Program. + + Later license versions may give you additional or different +permissions. However, no additional obligations are imposed on any +author or copyright holder as a result of your choosing to follow a +later version. + + 15. Disclaimer of Warranty. + + THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY +APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT +HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY +OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, +THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM +IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF +ALL NECESSARY SERVICING, REPAIR OR CORRECTION. + + 16. Limitation of Liability. + + IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS +THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY +GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE +USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF +DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD +PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), +EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF +SUCH DAMAGES. + + 17. Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + + END OF TERMS AND CONDITIONS + + How to Apply These Terms to Your New Programs + + If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + {one line to give the program's name and a brief idea of what it does.} + Copyright (C) {year} {name of author} + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + {project} Copyright (C) {year} {fullname} + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. diff --git a/sqlite3_howto/README.md b/sqlite3_howto/README.md new file mode 100644 index 0000000..9549f63 --- /dev/null +++ b/sqlite3_howto/README.md @@ -0,0 +1,784 @@ +## A thorough guide to SQLite database operations in Python + +_\-- written by Sebastian Raschka_ on March 7, 2014 + + + + + +![sqlite_python_logo.png](../Images/sqlite_python_logo.png) + + + + +* * * + +#### Sections + +• Connecting to an SQLite database +• Creating a new SQLite database + - Overview of SQLite data types + - A quick word on PRIMARY KEYS: +• Adding new columns +• Inserting and updating rows +• Creating unique indexes +• Querying the database - Selecting rows +• Security and injection attacks +• Date and time operations +• Printing a database summary +• Conclusion + +The complete Python code that I am using in this tutorial can be downloaded +from my GitHub repository: + + +* * * + + + +## Connecting to an SQLite database + +The sqlite3 that we will be using throughout this tutorial is part of the +Python Standard Library and is a nice and easy interface to SQLite databases: +There are no server processes involved, no configurations required, and no +other obstacles we have to worry about. + +In general, the only thing that needs to be done before we can perform any +operation on a SQLite database via Python's `sqlite3` module, is to open a +connection to an SQLite database file: + + + + import sqlite3 + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + +where the database file (`sqlite_file`) can reside anywhere on our disk, e.g., + + + + sqlite_file = '/Users/Sebastian/Desktop/my_db.sqlite' + + +Conveniently, a new database file (`.sqlite` file) will be created +automatically the first time we try to connect to a database. However, we have +to be aware that it won't have a table, yet. In the following section, we will +take a look at some example code of how to create a new SQLite database files +with tables for storing some data. + +To round up this section about connecting to a SQLite database file, there are +two more operations that are worth mentioning. If we are finished with our +operations on the database file, we have to close the connection via the +`.close()` method: + + + + conn.close() + + +And if we performed any operation on the database other than sending queries, +we need to commit those changes via the `.commit()` method before we close the +connection: + + + + conn.commit() + conn.close() + + + + +## Creating a new SQLite database + +Let us have a look at some example code to create a new SQLite database file +with two tables: One with and one without a PRIMARY KEY column (don't worry, +there is more information about PRIMARY KEYs further down in this section). + + + + mport sqlite3 + + sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file + table_name1 = 'my_table_1' # name of the table to be created + table_name2 = 'my_table_2' # name of the table to be created + new_field = 'my_1st_column' # name of the column + field_type = 'INTEGER' # column data type + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # Creating a new SQLite table with 1 column + c.execute('CREATE TABLE {tn} ({nf} {ft})'\ + .format(tn=table_name1, nf=new_field, ft=field_type)) + + # Creating a second table with 1 column and set it as PRIMARY KEY + # note that PRIMARY KEY column must consist of unique values! + c.execute('CREATE TABLE {tn} ({nf} {ft} PRIMARY KEY)'\ + .format(tn=table_name2, nf=new_field, ft=field_type)) + + # Committing changes and closing the connection to the database file + conn.commit() + conn.close() + + +Download the script: [create_new_db.py](https://raw.github.com/rasbt/python_sq +lite_code/master/code/create_new_db.py) + +* * * + +**Tip:** A handy tool to visualize and access SQLite databases is the free FireFox [SQLite Manager](https://addons.mozilla.org/en-US/firefox/addon/sqlite-manager/?src) add-on. Throughout this article, I will use this tool to provide screenshots of the database structures that we created below the corresponding code sections. + +* * * + + + + +![1_sqlite3_init_db.png](../Images/1_sqlite3_init_db.png) + +Using the code above, we created a new `.sqlite` database file with 2 tables. +Each table consists of currently one column only, which is of type INTEGER. + + + +* * * + +**Here is a quick overview of all data types that are supported by SQLite 3:** + + * INTEGER: A signed integer up to 8 bytes depending on the magnitude of the value. + * REAL: An 8-byte floating point value. + * TEXT: A text string, typically UTF-8 encoded (depending on the database encoding). + * BLOB: A blob of data (binary large object) for storing binary data. + * NULL: A NULL value, represents missing data or an empty cell. + +* * * + +Looking at the table above, You might have noticed that SQLite 3 has no +designated Boolean data type. However, this should not be an issue, since we +could simply re-purpose the INTEGER type to represent Boolean values (0 = +false, 1 = true). + + + +**A quick word on PRIMARY KEYS:** +In our example code above, we set our 1 column in the second table to PRIMARY +KEY. The advantage of a PRIMARY KEY index is a significant performance gain if +we use the PRIMARY KEY column as query for accessing rows in the table. Every +table can only have max. 1 PRIMARY KEY (single or multiple column(s)), and the +values in this column MUST be unique! But more on column indexing in the a +later section. + + + +## Adding new columns + +If we want to add a new column to an existing SQLite database table, we can +either leave the cells for each row empty (NULL value), or we can set a +default value for each cell, which is pretty convenient for certain +applications. +Let's have a look at some code: + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file + table_name = 'my_table_2' # name of the table to be created + id_column = 'my_1st_column' # name of the PRIMARY KEY column + new_column1 = 'my_2nd_column' # name of the new column + new_column2 = 'my_3nd_column' # name of the new column + column_type = 'TEXT' # E.g., INTEGER, TEXT, NULL, REAL, BLOB + default_val = 'Hello World' # a default value for the new column rows + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # A) Adding a new column without a row value + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct}"\ + .format(tn=table_name, cn=new_column1, ct=column_type)) + + # B) Adding a new column with a default row value + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct} DEFAULT '{df}'"\ + .format(tn=table_name, cn=new_column2, ct=column_type, df=default_val)) + + # Committing changes and closing the connection to the database file + conn.commit() + conn.close() + + +Download the script: [add_new_column.py](https://raw.github.com/rasbt/python_s +qlite_code/master/code/add_new_column.py) + + + +![2_sqlite3_add_col.png](../Images/2_sqlite3_add_col.png) + + +We just added 2 more columns (`my_2nd_column` and `my_3rd_column`) to +`my_table_2` of our SQLite database next to the PRIMARY KEY column +`my_1st_column`. +The difference between the two new columns is that we initialized +`my_3rd_column` with a default value (here:'Hello World'), which will be +inserted for every existing cell under this column and for every new row that +we are going to add to the table if we don't insert or update it with a +different value. + + + +## Inserting and updating rows + +Inserting and updating rows into an existing SQLite database table - next to +sending queries - is probably the most common database operation. The +Structured Query Language has a convenient `UPSERT` function, which is +basically just a merge between UPDATE and INSERT: It inserts new rows into a +database table with a value for the PRIMARY KEY column if it does not exist +yet, or updates a row for an existing PRIMARY KEY value. Unfortunately, this +convenient syntax is not supported by the more compact SQLite database +implementation that we are using here. However, there are some workarounds. +But let us first have a look at the example code: + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' + table_name = 'my_table_2' + id_column = 'my_1st_column' + column_name = 'my_2nd_column' + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # A) Inserts an ID with a specific value in a second column + try: + c.execute("INSERT INTO {tn} ({idf}, {cn}) VALUES (123456, 'test')".\ + format(tn=table_name, idf=id_column, cn=column_name)) + except sqlite3.IntegrityError: + print('ERROR: ID already exists in PRIMARY KEY column {}'.format(id_column)) + + # B) Tries to insert an ID (if it does not exist yet) + # with a specific value in a second column + c.execute("INSERT OR IGNORE INTO {tn} ({idf}, {cn}) VALUES (123456, 'test')".\ + format(tn=table_name, idf=id_column, cn=column_name)) + + # C) Updates the newly inserted or pre-existing entry + c.execute("UPDATE {tn} SET {cn}=('Hi World') WHERE {idf}=(123456)".\ + format(tn=table_name, cn=column_name, idf=id_column)) + + conn.commit() + conn.close() + + +Download the script: [update_or_insert_records.py](https://raw.github.com/rasb +t/python_sqlite_code/master/code/update_or_insert_records.py) + +![3_sqlite3_insert_update.png](../Images/3_sqlite3_insert_update.png) + +Both A) `INSERT` and B) `INSERT OR IGNORE` have in common that they append new +rows to the database if a given PRIMARY KEY does not exist in the database +table, yet. However, if we'd try to append a PRIMARY KEY value that is not +unique, a simple `INSERT` would raise an `sqlite3.IntegrityError` exception, +which can be either captured via a try-except statement (case A) or +circumvented by the SQLite call `INSERT OR IGNORE` (case B). This can be +pretty useful if we want to construct an `UPSERT` equivalent in SQLite. E.g., +if we want to add a dataset to an existing database table that contains a mix +between existing and new IDs for our PRIMARY KEY column. + + + +## Creating unique indexes + +Just like hashtable-datastructures, indexes function as direct pointers to our +data in a table for a particular column (i.e., the indexed column). For +example, the PRIMARY KEY column would have such an index by default. The +downside of indexes is that every row value in the column must be unique. +However, it is recommended and pretty useful to index certain columns if +possible, since it rewards us with a significant performance gain for the data +retrieval. +The example code below shows how to add such an unique index to an existing +column in an SQLite database table. And if we should decide to insert non- +unique values into a indexed column later, there is also a convenient way to +drop the index, which is also shown in the code below. + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file + table_name = 'my_table_2' # name of the table to be created + id_column = 'my_1st_column' # name of the PRIMARY KEY column + new_column = 'unique_names' # name of the new column + column_type = 'TEXT' # E.g., INTEGER, TEXT, NULL, REAL, BLOB + index_name = 'my_unique_index' # name for the new unique index + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # Adding a new column and update some record + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct}"\ + .format(tn=table_name, cn=new_column, ct=column_type)) + c.execute("UPDATE {tn} SET {cn}='sebastian_r' WHERE {idf}=123456".\ + format(tn=table_name, idf=id_column, cn=new_column)) + + # Creating an unique index + c.execute('CREATE INDEX {ix} on {tn}({cn})'\ + .format(ix=index_name, tn=table_name, cn=new_column)) + + # Dropping the unique index + # E.g., to avoid future conflicts with update/insert functions + c.execute('DROP INDEX {ix}'.format(ix=index_name)) + + # Committing changes and closing the connection to the database file + conn.commit() + conn.close() + + +Download the script: [create_unique_index.py](https://raw.github.com/rasbt/pyt +hon_sqlite_code/master/code/create_unique_index.py) + +![4_sqlite3_unique_index.png](../Images/4_sqlite3_unique_index.png) + + + + +## Querying the database - Selecting rows + +After we learned about how to create and modify SQLite databases, it's about +time for some data retrieval. The code below illustrates how we can retrieve +row entries for all or some columns if they match certain criteria. + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file + table_name = 'my_table_2' # name of the table to be queried + id_column = 'my_1st_column' + some_id = 123456 + column_2 = 'my_2nd_column' + column_3 = 'my_3rd_column' + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # 1) Contents of all columns for row that match a certain value in 1 column + c.execute('SELECT * FROM {tn} WHERE {cn}="Hi World"'.\ + format(tn=table_name, cn=column_2)) + all_rows = c.fetchall() + print('1):', all_rows) + + # 2) Value of a particular column for rows that match a certain value in column_1 + c.execute('SELECT ({coi}) FROM {tn} WHERE {cn}="Hi World"'.\ + format(coi=column_2, tn=table_name, cn=column_2)) + all_rows = c.fetchall() + print('2):', all_rows) + + # 3) Value of 2 particular columns for rows that match a certain value in 1 column + c.execute('SELECT {coi1},{coi2} FROM {tn} WHERE {coi1}="Hi World"'.\ + format(coi1=column_2, coi2=column_3, tn=table_name, cn=column_2)) + all_rows = c.fetchall() + print('3):', all_rows) + + # 4) Selecting only up to 10 rows that match a certain value in 1 column + c.execute('SELECT * FROM {tn} WHERE {cn}="Hi World" LIMIT 10'.\ + format(tn=table_name, cn=column_2)) + ten_rows = c.fetchall() + print('4):', ten_rows) + + # 5) Check if a certain ID exists and print its column contents + c.execute("SELECT * FROM {tn} WHERE {idf}={my_id}".\ + format(tn=table_name, cn=column_2, idf=id_column, my_id=some_id)) + id_exists = c.fetchone() + if id_exists: + print('5): {}'.format(id_exists)) + else: + print('5): {} does not exist'.format(some_id)) + + # Closing the connection to the database file + conn.close() + + +Download the script: [selecting_entries.py](https://raw.github.com/rasbt/pytho +n_sqlite_code/master/code/selecting_entries.py) + + +![4_sqlite3_unique_index.png](../Images/4_sqlite3_unique_index.png) + +if we use the `.fetchall()` method, we return a list of tuples from the +database query, where each tuple represents one row entry. The print output +for the 5 different cases shown in the code above would look like this (note +that we only have a table with 1 row here): + +![6_sqlite3_print_selecting_rows.png](../Images/6_sqlite3_print_selecting_rows +.png) + + + + +## Security and injection attacks + +So far, we have been using Python's string formatting method to insert +parameters like table and column names into the `c.execute()` functions. This +is fine if we just want to use the database for ourselves. However, this +leaves our database vulnerable to injection attacks. For example, if our +database would be part of a web application, it would allow hackers to +directly communicate with the database in order to bypass login and password +verification and steal data. +In order to prevent this, it is recommended to use `?` place holders in the +SQLite commands instead of the `%` formatting expression or the `.format()` +method, which we have been using in this tutorial. +For example, instead of using + + + + # 5) Check if a certain ID exists and print its column contents + c.execute("SELECT * FROM {tn} WHERE {idf}={my_id}".\ + format(tn=table_name, cn=column_2, idf=id_column, my_id=some_id)) + + +in the Querying the database - Selecting rows section above, we would want to +use the `?` placeholder for the queried column value and include the +variable(s) (here: `123456`), which we want to insert, as tuple at the end of +the `c.execute()` string. + + + + # 5) Check if a certain ID exists and print its column contents + c.execute("SELECT * FROM {tn} WHERE {idf}=?".\ + format(tn=table_name, cn=column_2, idf=id_column), (123456,)) + + +However, the problem with this approach is that it would only work for values, +not for column or table names. So what are we supposed to do with the rest of +the string if we want to protect ourselves from injection attacks? The easy +solution would be to refrain from using variables in SQLite queries whenever +possible, and if it cannot be avoided, we would want to use a function that +strips all non-alphanumerical characters from the stored content of the +variable, e.g., + + + + def clean_name(some_var): + return ''.join(char for char in some_var if char.isalnum()) + + + + +## Date and time operations + +SQLite inherited the convenient date and time operations from SQL, which are +one of my favorite features of the Structured Query Language: It does not only +allow us to insert dates and times in various different formats, but we can +also perform simple `+` and `-` arithmetic, for example to look up entries +that have been added xxx days ago. + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file + table_name = 'my_table_3' # name of the table to be created + id_field = 'id' # name of the ID column + date_col = 'date' # name of the date column + time_col = 'time'# name of the time column + date_time_col = 'date_time' # name of the date & time column + field_type = 'TEXT' # column data type + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # Creating a new SQLite table with 1 column + c.execute('CREATE TABLE {tn} ({fn} {ft} PRIMARY KEY)'\ + .format(tn=table_name, fn=id_field, ft=field_type)) + + # A) Adding a new column to save date insert a row with the current date + # in the following format: YYYY-MM-DD + # e.g., 2014-03-06 + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=date_col)) + # insert a new row with the current date and time, e.g., 2014-03-06 + c.execute("INSERT INTO {tn} ({idf}, {cn}) VALUES('some_id1', DATE('now'))"\ + .format(tn=table_name, idf=id_field, cn=date_col)) + + # B) Adding a new column to save date and time and update with the current time + # in the following format: HH:MM:SS + # e.g., 16:26:37 + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=time_col)) + # update row for the new current date and time column, e.g., 2014-03-06 16:26:37 + c.execute("UPDATE {tn} SET {cn}=TIME('now') WHERE {idf}='some_id1'"\ + .format(tn=table_name, idf=id_field, cn=time_col)) + + # C) Adding a new column to save date and time and update with current date-time + # in the following format: YYYY-MM-DD HH:MM:SS + # e.g., 2014-03-06 16:26:37 + c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=date_time_col)) + # update row for the new current date and time column, e.g., 2014-03-06 16:26:37 + c.execute("UPDATE {tn} SET {cn}=(CURRENT_TIMESTAMP) WHERE {idf}='some_id1'"\ + .format(tn=table_name, idf=id_field, cn=date_time_col)) + + # The database should now look like this: + # id date time date_time + # "some_id1" "2014-03-06" "16:42:30" "2014-03-06 16:42:30" + + # 4) Retrieve all IDs of entries between 2 date_times + c.execute("SELECT {idf} FROM {tn} WHERE {cn} BETWEEN '2013-03-06 10:10:10' AND '2015-03-06 10:10:10'".\ + format(idf=id_field, tn=table_name, cn=date_time_col)) + all_date_times = c.fetchall() + print('4) all entries between ~2013 - 2015:', all_date_times) + + # 5) Retrieve all IDs of entries between that are older than 1 day and 12 hrs + c.execute("SELECT {idf} FROM {tn} WHERE DATE('now') - {dc} >= 1 AND DATE('now') - {tc} >= 12".\ + format(idf=id_field, tn=table_name, dc=date_col, tc=time_col)) + all_1day12hrs_entries = c.fetchall() + print('5) entries older than 1 day:', all_1day12hrs_entries) + + # Committing changes and closing the connection to the database file + conn.commit() + conn.close() + + +Download the script: [date_time_ops.py](https://raw.github.com/rasbt/python_sq +lite_code/master/code/date_time_ops.py) + + + +![5_sqlite3_date_time.png](../Images/5_sqlite3_date_time.png) + + +Some of the really convenient functions that return the current time and date +are: + +* * * + + + DATE('now') # returns current date, e.g., 2014-03-06 + TIME('now') # returns current time, e.g., 10:10:10 + CURRENT_TIMESTAMP # returns current date and time, e.g., 2014-03-06 16:42:30 + # (or alternatively: DATETIME('now')) + + +* * * + +The screenshot below shows the print outputs of the code that we used to query +for entries that lie between a specified date interval using + + + + BETWEEN '2013-03-06 10:10:10' AND '2015-03-06 10:10:10' + + +and entries that are older than 1 day via + + + + WHERE DATE('now') - some_date + + +Note that we don't have to provide the complete time stamps here, the same +syntax applies to simple dates or simple times only, too. + +![5_sqlite3_date_time_2.png](../Images/5_sqlite3_date_time_2.png) + + + + +#### Update Mar 16, 2014: + + +If'd we are interested to calulate the hours between two `DATETIME()` +timestamps, we can could use the handy `STRFTIME()` function like this + + + + + SELECT (STRFTIME('%s','2014-03-14 14:51:00') - STRFTIME('%s','2014-03-16 14:51:00')) + / -3600 + + + +which would calculate the difference in hours between two dates in this +particular example above (here: `48`) in this case. +And to calculate the difference in hours between the current `DATETIME` and a +given `DATETIME` string, we could use the following SQLite syntax: + + + + + SELECT (STRFTIME('%s',DATETIME('now')) - STRFTIME('%s','2014-03-15 14:51:00')) / 3600 + + + + +## Retrieving column names + +In the previous two sections we have seen how we query SQLite databases for +data contents. Now let us have a look at how we retrieve its metadata (here: +column names): + + + + import sqlite3 + + sqlite_file = 'my_first_db.sqlite' + table_name = 'my_table_3' + + # Connecting to the database file + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + + # Retrieve column information + # Every column will be represented by a tuple with the following attributes: + # (id, name, type, notnull, default_value, primary_key) + c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + + # collect names in a list + names = [tup[1] for tup in c.fetchall()] + print(names) + # e.g., ['id', 'date', 'time', 'date_time'] + + # Closing the connection to the database file + conn.close() + + +Download the script: [get_columnnames.py](https://raw.github.com/rasbt/python_ +sqlite_code/master/code/get_columnnames.py) + +![7_sqlite3_get_colnames_1.png](../Images/7_sqlite3_get_colnames_1.png) + +Since we haven't created a PRIMARY KEY column for `my_table_3`, SQLite +automatically provides an indexed `rowid` column with unique ascending integer +values, which will be ignored in our case. Using the `PRAGMA TABLE_INFO()` +function on our table, we return a list of tuples, where each tuple contains +the following information about every column in the table: `(id, name, type, +notnull, default_value, primary_key)`. +So, in order to get the names of every column in our table, we only have to +grab the 2nd value in each tuple of the returned list, which can be done by + + + + names = [tup[1] for tup in c.fetchall()] + +after the `PRAGMA TABLE_INFO()` call. If we would print the contents of the +variable `names` now, the output would look like this: + +![7_sqlite3_get_colnames_2.png](../Images/7_sqlite3_get_colnames_2.png) + + + + +## Printing a database summary + +I hope we covered most of the basics about SQLite database operations in the +previous sections, and by now we should be well equipped to get some serious +work done using SQLite in Python. +Let me conclude this tutorial with an obligatory "last but not least" and a +convenient script to print a nice overview of SQLite database tables: + + + + import sqlite3 + + def connect(sqlite_file): + """ Make connection to an SQLite database file """ + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + return conn, c + + def close(conn): + """ Commit changes and close connection to the database """ + # conn.commit() + conn.close() + + def total_rows(cursor, table_name, print_out=False): + """ Returns the total number of rows in the database """ + c.execute('SELECT COUNT(*) FROM {}'.format(table_name)) + count = c.fetchall() + if print_out: + print('\nTotal rows: {}'.format(count[0][0])) + return count[0][0] + + def table_col_info(cursor, table_name, print_out=False): + """ + Returns a list of tuples with column informations: + (id, name, type, notnull, default_value, primary_key) + + """ + c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + info = c.fetchall() + + if print_out: + print("\nColumn Info:\nID, Name, Type, NotNull, DefaultVal, PrimaryKey") + for col in info: + print(col) + return info + + def values_in_col(cursor, table_name, print_out=True): + """ Returns a dictionary with columns as keys and the number of not-null + entries as associated values. + """ + c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + info = c.fetchall() + col_dict = dict() + for col in info: + col_dict[col[1]] = 0 + for col in col_dict: + c.execute('SELECT ({0}) FROM {1} WHERE {0} IS NOT NULL'.format(col, table_name)) + # In my case this approach resulted in a better performance than using COUNT + number_rows = len(c.fetchall()) + col_dict[col] = number_rows + if print_out: + print("\nNumber of entries per column:") + for i in col_dict.items(): + print('{}: {}'.format(i[0], i[1])) + return col_dict + + + if __name__ == '__main__': + + sqlite_file = 'my_first_db.sqlite' + table_name = 'my_table_3' + + conn, c = connect(sqlite_file) + total_rows(c, table_name, print_out=True) + table_col_info(c, table_name, print_out=True) + values_in_col(c, table_name, print_out=True) # slow on large data bases + + close(conn) + + +Download the script: [print_db_info.py](https://raw.github.com/rasbt/python_sq +lite_code/master/code/print_db_info.py) + +![8_sqlite3_print_db_info_1.png](../Images/8_sqlite3_print_db_info_1.png) + +![8_sqlite3_print_db_info_2.png](../Images/8_sqlite3_print_db_info_2.png) + + + +## Conclusion + +I really hope this tutorial was helpful to you to get started with SQLite +database operations via Python. I have been using the `sqlite3` module a lot +recently, and it has found its way into most of my programs for larger data +analyses. +Currently, I am working on a novel drug screening software that requires me to +store 3D structures and other functional data for ~13 million chemical +compounds, and SQLite has been an invaluable part of my program to quickly +store, query, analyze, and share my data. +Another smaller project that uses `sqlite3` in Python would be smilite, a +module to retrieve and compare SMILE strings of chemical compounds from the +free ZINC online database. If you are interested, you can check it out at: +. + +If you have any suggestions or questions, please don't hesitate to write me an +[ email](mailto:se.raschka@gmail.com) or leave a comment in the comment +section below! I am looking forward to your opinions and ideas, and I hope I +can improve and extend this tutorial in future. diff --git a/sqlite3_howto/code/add_new_column.py b/sqlite3_howto/code/add_new_column.py new file mode 100644 index 0000000..7e9fcd5 --- /dev/null +++ b/sqlite3_howto/code/add_new_column.py @@ -0,0 +1,28 @@ +# Sebastian Raschka, 2014 +# Adding a new column to an existing SQLite database + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file +table_name = 'my_table_2' # name of the table to be created +id_column = 'my_1st_column' # name of the PRIMARY KEY column +new_column1 = 'my_2nd_column' # name of the new column +new_column2 = 'my_3rd_column' # name of the new column +column_type = 'TEXT' # E.g., INTEGER, TEXT, NULL, REAL, BLOB +default_val = 'Hello World' # a default value for the new column rows + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# A) Adding a new column without a row value +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct}"\ + .format(tn=table_name, cn=new_column1, ct=column_type)) + +# B) Adding a new column with a default row value +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct} DEFAULT '{df}'"\ + .format(tn=table_name, cn=new_column2, ct=column_type, df=default_val)) + +# Committing changes and closing the connection to the database file +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/create_new_db.py b/sqlite3_howto/code/create_new_db.py new file mode 100644 index 0000000..df220da --- /dev/null +++ b/sqlite3_howto/code/create_new_db.py @@ -0,0 +1,27 @@ +# Sebastian Raschka, 2014 +# Creating a new SQLite database + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file +table_name1 = 'my_table_1' # name of the table to be created +table_name2 = 'my_table_2' # name of the table to be created +new_field = 'my_1st_column' # name of the column +field_type = 'INTEGER' # column data type + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# Creating a new SQLite table with 1 column +c.execute('CREATE TABLE {tn} ({nf} {ft})'\ + .format(tn=table_name1, nf=new_field, ft=field_type)) + +# Creating a second table with 1 column and set it as PRIMARY KEY +# note that PRIMARY KEY column must consist of unique values! +c.execute('CREATE TABLE {tn} ({nf} {ft} PRIMARY KEY)'\ + .format(tn=table_name2, nf=new_field, ft=field_type)) + +# Committing changes and closing the connection to the database file +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/create_unique_index.py b/sqlite3_howto/code/create_unique_index.py new file mode 100644 index 0000000..28f56a8 --- /dev/null +++ b/sqlite3_howto/code/create_unique_index.py @@ -0,0 +1,34 @@ +# Sebastian Raschka, 2014 +# Creating an index on a column with unique! values +# Boosts performance for data base operations. + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file +table_name = 'my_table_2' # name of the table to be created +id_column = 'my_1st_column' # name of the PRIMARY KEY column +new_column = 'unique_names' # name of the new column +column_type = 'TEXT' # E.g., INTEGER, TEXT, NULL, REAL, BLOB +index_name = 'my_unique_index' # name for the new unique index + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# Adding a new column and update some record +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}' {ct}"\ + .format(tn=table_name, cn=new_column, ct=column_type)) +c.execute("UPDATE {tn} SET {cn}='sebastian_r' WHERE {idf}=123456".\ + format(tn=table_name, idf=id_column, cn=new_column)) + +# Creating an unique index +c.execute('CREATE INDEX {ix} on {tn}({cn})'\ + .format(ix=index_name, tn=table_name, cn=new_column)) + +# Dropping the unique index +# E.g., to avoid future conflicts with update/insert functions +c.execute('DROP INDEX {ix}'.format(ix=index_name)) + +# Committing changes and closing the connection to the database file +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/date_time_ops.py b/sqlite3_howto/code/date_time_ops.py new file mode 100644 index 0000000..ddb8547 --- /dev/null +++ b/sqlite3_howto/code/date_time_ops.py @@ -0,0 +1,69 @@ +# Sebastian Raschka, 03/2014 +# Date and Time operations in sqlite3 + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file +table_name = 'my_table_3' # name of the table to be created +id_field = 'id' # name of the ID column +date_col = 'date' # name of the date column +time_col = 'time'# name of the time column +date_time_col = 'date_time' # name of the date & time column +field_type = 'TEXT' # column data type + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# Creating a new SQLite table with 1 column +c.execute('CREATE TABLE {tn} ({fn} {ft} PRIMARY KEY)'\ + .format(tn=table_name, fn=id_field, ft=field_type)) + + +# 1) Adding a new column to save date insert a row with the current date +# in the following format: YYYY-MM-DD +# e.g., 2014-03-06 +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=date_col)) +# insert a new row with the current date and time, e.g., 2014-03-06 +c.execute("INSERT INTO {tn} ({idf}, {cn}) VALUES('some_id1', DATE('now'))"\ + .format(tn=table_name, idf=id_field, cn=date_col)) + + +# 2) Adding a new column to save date and time and update with the current time +# in the following format: HH:MM:SS +# e.g., 16:26:37 +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=time_col)) +# update row for the new current date and time column, e.g., 2014-03-06 16:26:37 +c.execute("UPDATE {tn} SET {cn}=TIME('now') WHERE {idf}='some_id1'"\ + .format(tn=table_name, idf=id_field, cn=time_col)) + +# 3) Adding a new column to save date and time and update with current date-time +# in the following format: YYYY-MM-DD HH:MM:SS +# e.g., 2014-03-06 16:26:37 +c.execute("ALTER TABLE {tn} ADD COLUMN '{cn}'"\ + .format(tn=table_name, cn=date_time_col)) +# update row for the new current date and time column, e.g., 2014-03-06 16:26:37 +c.execute("UPDATE {tn} SET {cn}=(CURRENT_TIMESTAMP) WHERE {idf}='some_id1'"\ + .format(tn=table_name, idf=id_field, cn=date_time_col)) + +# Database should now look like this: +# id date time date_time +# "some_id1" "2014-03-06" "16:42:30" "2014-03-06 16:42:30" + +# 4) Retrieve all IDs of entries between 2 date_times +c.execute("SELECT {idf} FROM {tn} WHERE {cn} BETWEEN '2013-03-06 10:10:10' AND '2015-03-06 10:10:10'".\ + format(idf=id_field, tn=table_name, cn=date_time_col)) +all_date_times = c.fetchall() +print('4) all entries between ~2013 - 2015:', all_date_times) + +# 5) Retrieve all IDs of entries between that are older than 1 day and 12 hrs +c.execute("SELECT {idf} FROM {tn} WHERE DATE('now') - {dc} >= 1 AND DATE('now') - {tc} >= 12".\ + format(idf=id_field, tn=table_name, dc=date_col, tc=time_col)) +all_1day12hrs_entries = c.fetchall() +print('5) entries older than 1 day:', all_1day12hrs_entries) + +# Committing changes and closing the connection to the database file +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/get_columnnames.py b/sqlite3_howto/code/get_columnnames.py new file mode 100644 index 0000000..f02142e --- /dev/null +++ b/sqlite3_howto/code/get_columnnames.py @@ -0,0 +1,24 @@ +# Sebastian Raschka, 2014 +# Getting column names of an SQLite database table + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' +table_name = 'my_table_3' + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# Retrieve column information +# Every column will be represented by a tuple with the following attributes: +# (id, name, type, notnull, default_value, primary_key) +c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + +# collect names in a list +names = [tup[1] for tup in c.fetchall()] +print(names) +# e.g., ['id', 'date', 'time', 'date_time'] + +# Closing the connection to the database file +conn.close() diff --git a/sqlite3_howto/code/print_db_info.py b/sqlite3_howto/code/print_db_info.py new file mode 100644 index 0000000..22b72a8 --- /dev/null +++ b/sqlite3_howto/code/print_db_info.py @@ -0,0 +1,91 @@ +# Sebastian Raschka 2014 +# Prints Information of a SQLite database. + +# E.g., +# +""" +Total rows: 1 + +Column Info: +ID, Name, Type, NotNull, DefaultVal, PrimaryKey +(0, 'id', 'TEXT', 0, None, 1) +(1, 'date', '', 0, None, 0) +(2, 'time', '', 0, None, 0) +(3, 'date_time', '', 0, None, 0) + +Number of entries per column: +date: 1 +date_time: 1 +id: 1 +time: 1 +""" + +import sqlite3 + +def connect(sqlite_file): + """ Make connection to an SQLite database file """ + conn = sqlite3.connect(sqlite_file) + c = conn.cursor() + return conn, c + +def close(conn): + """ Commit changes and close connection to the database """ + #conn.commit() + conn.close() + +def total_rows(cursor, table_name, print_out=False): + """ Returns the total number of rows in the database """ + c.execute('SELECT COUNT(*) FROM {}'.format(table_name)) + count = c.fetchall() + if print_out: + print('\nTotal rows: {}'.format(count[0][0])) + return count[0][0] + +def table_col_info(cursor, table_name, print_out=False): + """ + Returns a list of tuples with column informations: + (id, name, type, notnull, default_value, primary_key) + + """ + c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + info = c.fetchall() + + if print_out: + print("\nColumn Info:\nID, Name, Type, NotNull, DefaultVal, PrimaryKey") + for col in info: + print(col) + return info + +def values_in_col(cursor, table_name, print_out=True): + """ Returns a dictionary with columns as keys and the number of not-null + entries as associated values. + """ + c.execute('PRAGMA TABLE_INFO({})'.format(table_name)) + info = c.fetchall() + col_dict = dict() + for col in info: + col_dict[col[1]] = 0 + for col in col_dict: + c.execute('SELECT ({0}) FROM {1} WHERE {0} IS NOT NULL'.format(col, table_name)) + # In my case this approach resulted in a better performance than using COUNT + number_rows = len(c.fetchall()) + col_dict[col] = number_rows + if print_out: + print("\nNumber of entries per column:") + for i in col_dict.items(): + print('{}: {}'.format(i[0], i[1])) + return col_dict + + +if __name__ == '__main__': + + sqlite_file = 'my_first_db.sqlite' + table_name = 'my_table_3' + + conn, c = connect(sqlite_file) + total_rows(c, table_name, print_out=True) + table_col_info(c, table_name, print_out=True) + values_in_col(c, table_name, print_out=True) # slow on large data bases + + close(conn) + diff --git a/sqlite3_howto/code/selecting_entries.py b/sqlite3_howto/code/selecting_entries.py new file mode 100644 index 0000000..0ba8e19 --- /dev/null +++ b/sqlite3_howto/code/selecting_entries.py @@ -0,0 +1,51 @@ +# Sebastian Raschka, 2014 +# Selecting rows from an existing SQLite database + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' # name of the sqlite database file +table_name = 'my_table_2' # name of the table to be queried +id_column = 'my_1st_column' +some_id = 123456 +column_2 = 'my_2nd_column' +column_3 = 'my_3rd_column' + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + +# 1) Contents of all columns for row that match a certain value in 1 column +c.execute('SELECT * FROM {tn} WHERE {cn}="Hi World"'.\ + format(tn=table_name, cn=column_2)) +all_rows = c.fetchall() +print('1):', all_rows) + +# 2) Value of a particular column for rows that match a certain value in column_1 +c.execute('SELECT ({coi}) FROM {tn} WHERE {cn}="Hi World"'.\ + format(coi=column_2, tn=table_name, cn=column_2)) +all_rows = c.fetchall() +print('2):', all_rows) + +# 3) Value of 2 particular columns for rows that match a certain value in 1 column +c.execute('SELECT {coi1},{coi2} FROM {tn} WHERE {coi1}="Hi World"'.\ + format(coi1=column_2, coi2=column_3, tn=table_name, cn=column_2)) +all_rows = c.fetchall() +print('3):', all_rows) + +# 4) Selecting only up to 10 rows that match a certain value in 1 column +c.execute('SELECT * FROM {tn} WHERE {cn}="Hi World" LIMIT 10'.\ + format(tn=table_name, cn=column_2)) +ten_rows = c.fetchall() +print('4):', ten_rows) + +# 5) Check if a certain ID exists and print its column contents +c.execute("SELECT * FROM {tn} WHERE {idf}=?".\ + format(tn=table_name, cn=column_2, idf=id_column), (123456,)) +id_exists = c.fetchone() +if id_exists: + print('5): {}'.format(id_exists)) +else: + print('5): {} does not exist'.format(some_id)) + +# Closing the connection to the database file +conn.close() diff --git a/sqlite3_howto/code/update_or_insert_records.py b/sqlite3_howto/code/update_or_insert_records.py new file mode 100644 index 0000000..37292a5 --- /dev/null +++ b/sqlite3_howto/code/update_or_insert_records.py @@ -0,0 +1,35 @@ +# Sebastian Raschka, 2014 +# Update records or insert them if they don't exist. +# Note that this is a workaround to accomodate for missing +# SQL features in SQLite. + +import sqlite3 + +sqlite_file = 'my_first_db.sqlite' +table_name = 'my_table_2' +id_column = 'my_1st_column' +column_name = 'my_2nd_column' + +# Connecting to the database file +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + + +# A) Inserts an ID with a specific value in a second column +try: + c.execute("INSERT INTO {tn} ({idf}, {cn}) VALUES (123456, 'test')".\ + format(tn=table_name, idf=id_column, cn=column_name)) +except sqlite3.IntegrityError: + print('ERROR: ID already exists in PRIMARY KEY column {}'.format(id_column)) + +# B) Tries to insert an ID (if it does not exist yet) +# with a specific value in a second column +c.execute("INSERT OR IGNORE INTO {tn} ({idf}, {cn}) VALUES (123456, 'test')".\ + format(tn=table_name, idf=id_column, cn=column_name)) + +# C) Updates the newly inserted or pre-existing entry +c.execute("UPDATE {tn} SET {cn}=('Hi World') WHERE {idf}=(123456)".\ + format(tn=table_name, cn=column_name, idf=id_column)) + +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/updating_rows.py b/sqlite3_howto/code/updating_rows.py new file mode 100644 index 0000000..5c4f762 --- /dev/null +++ b/sqlite3_howto/code/updating_rows.py @@ -0,0 +1,50 @@ +# Sebastian Raschka, 2014 +# Updating rows in an existing SQLite database + +import sqlite3 + +sqlite_file = '' +table_name = '' +column_name_1 = '' +column_name_2 = '' +column_name_3 = '' +value_1 = 'hello world' +value_2 = 12345 + +conn = sqlite3.connect(sqlite_file) +c = conn.cursor() + + +# A.1) Updating all rows for a single column + +c.execute('UPDATE {dn} SET {cn1}={v1}'.\ + format(dn=table_name, cn1=column_name_1, v1=value1) + + +# A.2) Updating all rows for 2 columns (same for multiple columns) + +c.execute('UPDATE {dn} SET {cn1}={v1}, {cn2}={v2}'.\ + format(dn=table_name, cn1=column_name_1, cn2=column_name_2, + v1=value1, v2=value2) + + + + +# B.1) Updating specific rows that meet a certain criterion +# here: update column_1 with value_1 if row has value_2 in column_2 + +c.execute('UPDATE {dn} SET {cn1}={v1} WHERE {cn2}={v2}'.\ + format(dn=table_name, cn1=column_name_1, v1=value1) + + +# B.2) Updating specific rows that meet multiple criteria +# here: update column_1 with value_1 +# if row has value_2 in column_2 +# and if row has value = 1 in column_3 + +c.execute('UPDATE {dn} SET {cn1}={v1} WHERE {cn2}={v2} AND {cn3}=1'.\ + format(dn=table_name, cn1=column_name_1, v1=value1, cn3=column_name_3) + + +conn.commit() +conn.close() diff --git a/sqlite3_howto/code/write_from_sqlite.py b/sqlite3_howto/code/write_from_sqlite.py new file mode 100644 index 0000000..f3f41a4 --- /dev/null +++ b/sqlite3_howto/code/write_from_sqlite.py @@ -0,0 +1,102 @@ +import sqlite3 + +def create_col_index(db_name, table_name, column_name, index_name): + ''' + Creates a column index on a SQLite table. + + Keyword arguments: + db_name (str): Path of the .sqlite database file. + table_name (str): Name of the target table in the SQLite file. + condition (str): Condition for querying the SQLite database table. + column_name (str): Name of the column for which the index is created. + + ''' + + # Connecting to the database file + conn = sqlite3.connect(db_name) + c = conn.cursor() + + # Creating the index + c.execute('CREATE INDEX {} ON {} ({})'.format(index_name, table_name, column_name)) + + # Save index and close the connection to the database + conn.commit() + conn.close() + + + +def drop_col_index(db_name, index_name): + ''' + Drops a column index from a SQLite table. + + Keyword arguments: + db_name (str): Path of the .sqlite database file. + table_name (str): Name of the target table in the SQLite file. + condition (str): Condition for querying the SQLite database table. + column_name (str): Name of the column for which the index is dropped. + + ''' + + # Connecting to the database file + conn = sqlite3.connect(db_name) + c = conn.cursor() + + # Drops the index + c.execute('DROP INDEX {}'.format(index_name)) + + # Save index and close the connection to the database + conn.commit() + conn.close() + + + +def write_from_query(db_name, table_name, condition, content_column, out_file, fetchmany=False): + ''' + Writes contents from a SQLite database column to an output file + + Keyword arguments: + db_name (str): Path of the .sqlite database file. + table_name (str): Name of the target table in the SQLite file. + condition (str): Condition for querying the SQLite database table. + content_column (str): Name of the column that contains the content for the output file. + out_file (str): Path of the output file that will be written. + + ''' + # Connecting to the database file + conn = sqlite3.connect(db_name) + c = conn.cursor() + + # Querying the database and writing the output file + + + # A) using .fetchmany(); recommended for larger databases + if fetchmany: + c.execute('SELECT ({}) FROM {} WHERE {}'.format(content_column, table_name, condition)) + with open(out_file, 'w') as outf: + results = c.fetchmany(fetchmany) + while results: + for row in results: + outf.write(row[0]) + results = c.fetchmany(fetchmany) + + # B) simple .execute() loop + else: + c.execute('SELECT ({}) FROM {} WHERE {}'.format(content_column, table_name, condition)) + with open(out_file, 'w') as outf: + for row in c: + outf.write(row[0]) + + # Closing the connection to the database + conn.close() + +if __name__ == '__main__': + write_from_query( + db_name='my_db.sqlite', + table_name='my_table', + condition='variable1=1 AND variable2<=5 AND variable3="Zinc_Plus"', + content_column='variable4', + out_file='sqlite_out.txt' + ) + + +