Transactional Stored Procedures in MySQL

Executing multiple SQL statements in a transactional manner within a stored procedure ensures either all the statements execute successfully or none execute at all. This behavior is critical for maintaining data consistency and integrity. Here's how you can achieve transactions in your MySQL stored procedure:

Syntax Error Correction

In your provided code snippet, there are two syntax errors that are preventing the stored procedure from becoming transactional. The correct syntax is as follows:

DECLARE EXIT HANDLER FOR SQLEXCEPTION, SQLWARNING
BEGIN
    ROLLBACK;
END;

This code declares an exit handler that will automatically roll back any changes if an SQL exception or warning occurs during the execution of the stored procedure. The commas between the conditions for the exit handler and the semicolon at the end of the DECLARE statement are crucial for the proper functioning of the stored procedure.

Example

Once the syntax errors have been corrected, the stored procedure can be made transactional by enclosing the SQL statements within a START TRANSACTION...COMMIT block. Here's an example of a transactional stored procedure:

BEGIN

DECLARE EXIT HANDLER FOR SQLEXCEPTION, SQLWARNING
BEGIN
    ROLLBACK;
END;

START TRANSACTION;

    -- Your SQL statements here

COMMIT;

END

Usage

To use the transactional stored procedure, simply call it from your application code as a regular stored procedure. If all the SQL statements within the stored procedure execute successfully, the COMMIT statement will make these changes permanent in the database. If any SQL exception or warning occurs, the ROLLBACK statement will automatically undo all the changes.