Python Tutorial ( PDFDrive )
COMMIT Operation: Commit is the operation, which gives a green signal to database to finalize the changes, and after this operation,no change can be reverted back.Here is a simple example to call commit method.db.commit()ROLLBACK Operation: If you are not satisfied with one or more of the changes and you want to revert back those changes completely,then use rollback() method.Here is a simple example to call rollback() method.db.rollback()Disconnecting Database: To disconnect Database connection, use close() method.db.close()If the connection to a database is closed by the user with the close() method, any outstanding transactions arerolled back by the DB. However, instead of depending on any of DB lower level implementation details, yourapplication would be better off calling commit or rollback explicitly.Handling Errors: There are many sources of errors. A few examples are a syntax error in an executed SQL statement, aconnection failure, or calling the fetch method for an already canceled or finished statement handle.The DB API defines a number of errors that must exist in each database module. The following table lists theseexceptions.ExceptionWarningErrorInterfaceErrorDatabaseErrorDataErrorOperationalErrorIntegrityErrorInternalErrorDescriptionUsed for non-fatal issues. Must subclass StandardError.Base class for errors. Must subclass StandardError.Used for errors in the database module, not the database itself. Must subclassError.Used for errors in the database. Must subclass Error.Subclass of DatabaseError that refers to errors in the data.Subclass of DatabaseError that refers to errors such as the loss of a connection tothe database. These errors are generally outside of the control of the Pythonscripter.Subclass of DatabaseError for situations that would damage the relational integrity,such as uniqueness constraints or foreign keys.Subclass of DatabaseError that refers to errors internal to the database module,such as a cursor no longer being active.TUTORIALS POINT Simply Easy Learning
ProgrammingErrorSubclass of DatabaseError that refers to errors such as a bad table name andother things that can safely be blamed on you.NotSupportedError Subclass of DatabaseError that refers to trying to call unsupported functionality.Your Python scripts should handle these errors, but before using any of the above exceptions, make sure yourMySQLdb has support for that exception. You can get more information about them by reading the DB API 2.0specification.TUTORIALS POINT Simply Easy Learning
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ProgrammingError
Subclass of DatabaseError that refers to errors such as a bad table name and
other things that can safely be blamed on you.
NotSupportedError Subclass of DatabaseError that refers to trying to call unsupported functionality.
Your Python scripts should handle these errors, but before using any of the above exceptions, make sure your
MySQLdb has support for that exception. You can get more information about them by reading the DB API 2.0
specification.
TUTORIALS POINT
Simply Easy Learning
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