MySQL - Trigger for updating same table after insert

问题

Here\'s what I\'m trying to do:

When there\'s a new INSERT into the table ACCOUNTS, I need to update the row in ACCOUNTS where pk = NEW.edit_on by setting status=\'E\' to denote that the particular (old) account has been edited.

DELIMITER $$

DROP TRIGGER IF EXISTS `setEditStatus`$$
CREATE TRIGGER `setEditStatus` AFTER INSERT on ACCOUNTS
FOR EACH ROW BEGIN
    update ACCOUNTS set status=\'E\' where ACCOUNTS.pk = NEW.edit_on ;
END$$

DELIMITER ;

The requirement is NOT that I manipulate the newly inserted column, but an already existing column with pk = NEW.edit_on

However, I can\'t update the same table: Can\'t update table ACCOUNTS ... already used by the statement that invoked this trigger

Please suggest a workaround

PS: I have already gone through Updating table in trigger after update on the same table, Insert into same table trigger mysql, Update with after insert trigger on same table and mysql trigger with insert and update after insert on table but they dont seem to answer my question.

Edit

ACCOUNTS Table:

CREATE TABLE  `ACCOUNTS` (
  `pk` bigint(10) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` bigint(9) unsigned NOT NULL,
  `edit_on` bigint(10) unsigned DEFAULT NULL,
  `status` varchar(1) NOT NULL DEFAULT \'A\',
  PRIMARY KEY (`pk`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=2147483726 DEFAULT CHARSET=latin1

回答1:

It seems that you can't do all this in a trigger. According to the documentation:

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.

According to this answer, it seems that you should:

create a stored procedure, that inserts into/Updates the target table, then updates the other row(s), all in a transaction.

With a stored proc you'll manually commit the changes (insert and update). I haven't done this in MySQL, but this post looks like a good example.

回答2:

This is how i update a row in the same table on insert

activationCode and email are rows in the table USER. On insert i don't specify a value for activationCode, it will be created on the fly by mysql.

Change 'username' with your mysql username and 'db_name' with your db name.

CREATE DEFINER=`username`@`localhost` 
       TRIGGER `db_name`.`user_BEFORE_INSERT` 
       BEFORE INSERT ON `user` 
       FOR EACH ROW
         BEGIN
            SET new.activationCode = MD5(new.email);
         END

回答3:

Had the same problem but had to update a column with the id that was about to enter, so you can make an update should be done BEFORE and AFTER not BEFORE had no id so I did this trick

DELIMITER $$
DROP TRIGGER IF EXISTS `codigo_video`$$
CREATE TRIGGER `codigo_video` BEFORE INSERT ON `videos` 
FOR EACH ROW BEGIN
    DECLARE ultimo_id, proximo_id INT(11);
    SELECT id INTO ultimo_id FROM videos ORDER BY id DESC LIMIT 1;
    SET proximo_id = ultimo_id+1;
    SET NEW.cassette = CONCAT(NEW.cassette, LPAD(proximo_id, 5, '0'));
END$$
DELIMITER ;

回答4:

On the last entry; this is another trick:

SELECT AUTO_INCREMENT FROM information_schema.tables WHERE table_schema = ... and table_name = ...

回答5:

Instead you can use before insert and get max pkid for the particular table and then update the maximium pkid table record.

回答6:

DELIMITER $$

DROP TRIGGER IF EXISTS `setEditStatus`$$
CREATE TRIGGER `setEditStatus` **BEFORE** INSERT on ACCOUNTS
FOR EACH ROW BEGIN

    SET NEW.STATUS = 'E';

END$$

DELIMITER ;

来源：https://stackoverflow.com/questions/12877732/mysql-trigger-for-updating-same-table-after-insert

标签

mysql

database-trigger