Question

Well, I have researched and have not found a solution to the following problem 'SQL Error (1442): Can not update table' messages' in stored function / trigger because it is already used by statement Which invoked this stored function / trigger. `

My trigger is created, only when I run the INSERT on the table of messages, this error is thrown, my trigger is

DELIMITER $$ 
DROP TRIGGER IF EXISTS `onMessage` ;
CREATE TRIGGER `onMessage` BEFORE INSERT ON `messages` FOR EACH ROW 
BEGIN
       UPDATE `users` SET `users`.`messages` = ( `users`.`messages` + 1 ) 
       WHERE `users`.`uid` = NEW.uid ;
       DELETE FROM `messages` WHERE `date` < ( NOW( ) - INTERVAL 1 MINUTE ) ;
END ;
$$
DELIMITER ;

Answer 1

This is a restriction in the use of triggers.

From the MySql documentations:

Within a stored function or trigger, it is not permitted to modify a table that is already being used (for reading or writing) by the statement that invoked the function or trigger.