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103 lines
3.1 KiB
Python
103 lines
3.1 KiB
Python
import sqlite3
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def create_col_index(db_name, table_name, column_name, index_name):
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'''
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Creates a column index on a SQLite table.
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Keyword arguments:
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db_name (str): Path of the .sqlite database file.
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table_name (str): Name of the target table in the SQLite file.
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condition (str): Condition for querying the SQLite database table.
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column_name (str): Name of the column for which the index is created.
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'''
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# Connecting to the database file
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conn = sqlite3.connect(db_name)
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c = conn.cursor()
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# Creating the index
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c.execute('CREATE INDEX {} ON {} ({})'.format(index_name, table_name, column_name))
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# Save index and close the connection to the database
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conn.commit()
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conn.close()
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def drop_col_index(db_name, index_name):
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'''
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Drops a column index from a SQLite table.
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Keyword arguments:
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db_name (str): Path of the .sqlite database file.
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table_name (str): Name of the target table in the SQLite file.
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condition (str): Condition for querying the SQLite database table.
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column_name (str): Name of the column for which the index is dropped.
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'''
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# Connecting to the database file
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conn = sqlite3.connect(db_name)
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c = conn.cursor()
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# Drops the index
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c.execute('DROP INDEX {}'.format(index_name))
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# Save index and close the connection to the database
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conn.commit()
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conn.close()
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def write_from_query(db_name, table_name, condition, content_column, out_file, fetchmany=False):
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'''
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Writes contents from a SQLite database column to an output file
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Keyword arguments:
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db_name (str): Path of the .sqlite database file.
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table_name (str): Name of the target table in the SQLite file.
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condition (str): Condition for querying the SQLite database table.
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content_column (str): Name of the column that contains the content for the output file.
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out_file (str): Path of the output file that will be written.
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'''
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# Connecting to the database file
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conn = sqlite3.connect(db_name)
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c = conn.cursor()
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# Querying the database and writing the output file
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# A) using .fetchmany(); recommended for larger databases
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if fetchmany:
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c.execute('SELECT ({}) FROM {} WHERE {}'.format(content_column, table_name, condition))
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with open(out_file, 'w') as outf:
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results = c.fetchmany(fetchmany)
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while results:
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for row in results:
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outf.write(row[0])
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results = c.fetchmany(fetchmany)
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# B) simple .execute() loop
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else:
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c.execute('SELECT ({}) FROM {} WHERE {}'.format(content_column, table_name, condition))
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with open(out_file, 'w') as outf:
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for row in c:
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outf.write(row[0])
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# Closing the connection to the database
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conn.close()
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if __name__ == '__main__':
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write_from_query(
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db_name='my_db.sqlite',
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table_name='my_table',
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condition='variable1=1 AND variable2<=5 AND variable3="Zinc_Plus"',
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content_column='variable4',
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out_file='sqlite_out.txt'
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)
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