Learn how to use Rollback in MySQL stored procedures. Our MySQL Support team is here to help you with your questions and concerns.

How to Use Rollback in MySQL Stored Procedures

A stored procedure in MySQL is a collection of SQL statements stored and executed on the server. With transactions, rollback helps maintain data integrity by undoing changes if an error occurs or specific conditions are met.

A transaction is a sequence of one or more SQL operations executed as a single unit. They make sure that either all operations are successful or none of them are.

The Commit option makes all changes made during the transaction permanent.

Additionally, Rollback reverts all changes made during the transaction.

How to Use Rollback in Stored Procedures

• Starting a Transaction

  Start a transaction using the `START TRANSACTION` or `BEGIN` statement.
• Committing a Transaction

  Save all changes made during the transaction with the `COMMIT` statement.
• Rolling Back a Transaction

  Undo all changes made during the transaction using the `ROLLBACK` statement.
• Explicit Transaction Boundaries

  We can define the boundaries of a transaction using the `START TRANSACTION` and `COMMIT` statements in the stored procedure.

  SQL statements executed after `START TRANSACTION` and before `COMMIT` are part of the transaction.

  If an error occurs during the execution of any statement within this block, the entire transaction can be rolled back using `ROLLBACK`. This ensures data consistency by undoing all changes made within the transaction.

Exception Handling with DECLARE and HANDLER

MySQL allows defining exception handlers using `DECLARE` and `HANDLER` statements. We can define a handler specifically for `SQLEXCEPTION` to catch any errors that might occur within our stored procedure. Within the handler, we can execute a `ROLLBACK` statement to undo changes if an error is encountered.

Here is an example of a stored procedure that uses transaction management and rollback:

DELIMITER //
CREATE PROCEDURE st_transaction_Rollback()
BEGIN
DECLARE exit handler for sqlexception
BEGIN
ROLLBACK;
END;
DECLARE exit handler for sqlwarning
BEGIN
ROLLBACK;
END;
START TRANSACTION;
INSERT INTO employee.tbl(name) VALUES();
UPDATE employee.tbl SET name = 'JohnDoe' WHERE id = 5;
COMMIT;
END //
DELIMITER ;


We can execute the stored procedure as seen here:

CALL st_transaction_Rollback();

Furthermore, we can verify the data with the SELECT command.

Using rollback in MySQL stored procedures helps maintain data integrity, especially when dealing with multiple related operations that need to be executed as a single unit. With proper transaction management and exception handling, we can make sure that our data remains consistent and reliable.

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Conclusion

In brief, our Support Experts demonstrated how to use Rollback in MySQL stored procedures.