How to throw an error in MySql procedure?

Question

What is the mechanism to force the MySQL to throw an error within the stored procedure?

I have a procedure which call s another function:

PREPARE my_         


        

Answer 1

Yes, there is: use the SIGNAL keyword.

Answer 2

You may use following stored procedure to emulate error-throwing:

CREATE PROCEDURE `raise`(`errno` BIGINT UNSIGNED, `message` VARCHAR(256))
BEGIN
SIGNAL SQLSTATE
    'ERR0R'
SET
    MESSAGE_TEXT = `message`,
    MYSQL_ERRNO = `errno`;
END

Example:

CALL `raise`(1356, 'My Error Message');