Deleting Data From Oracle Database in Python

Summary: in this tutorial, you will learn how to use the Python cx_Oracle API to delete data from a table.

To delete data from a table, you use the following steps:

• First, connect to the Oracle Database by creating a new Connection object.
• Second, create a new Cursor object from the Connection object by calling the Connection.Cursor() method.
• Third, execute a DELETE statement by calling the Cursor.execute() method.
• Fourth, call the Connection.commit() method to apply the changes to the database. If you forget to call the Connection.commit() method, you will see that the change will not take effect.
• Finally, release the Cursor and Connection objects by calling the Cursor.close() and Connection.close() method respectively. You can also use the with block to release these objects automatically.

The following code illustrates how to delete a row from the billing_headers table based on a specific billing number.

import cx_Oracle
import config as cfg


def delete_billing(billing_no, amount):
    """
    Delete a billing based on a billing no.
    :param billing_no:
    :return:
    """
    sql = ('delete from billing_headers '
           'where billing_no = :billing_no')
    try:
        # establish a new connection
        with cx_Oracle.connect(cfg.username,
                            cfg.password,
                            cfg.dsn,
                            encoding=cfg.encoding) as connection:
            # create a cursor
            with connection.cursor() as cursor:
                # execute the insert statement
                cursor.execute(sql, [amount, billing_no])
                # commit the change
                connection.commit()
    except cx_Oracle.Error as error:
        print(error)


if __name__ == '__main__':
    delete_billing(1)

Here are the contents of the billing_headers table after executing the program:

SELECT * FROM billing_headers;

As you can see clearly from the output, the row whose billing_no is 1 has been removed. It means that the program works as expected.

If you have not following the previous tutorials, you can use the config.py module:

username = 'OT'
password = '<password>'
dsn = 'localhost/pdborcl'
port = 1512
encoding = 'UTF-8'

And the following script to create the billing_headers table:

CREATE TABLE billing_headers(
    billing_no NUMBER GENERATED BY DEFAULT AS IDENTITY,
    billing_date DATE NOT NULL,
    amount NUMBER(19,4) DEFAULT 0 NOT NULL,
    customer_id NUMBER NOT NULL,
    note VARCHAR2(100),
    PRIMARY KEY(billing_no)
);

In this tutorial, you have learned how to use the Python cx_Oracle API to delete data in a table.