How to create a before update trigger for 2 fields "expected_hash" and "identify_hash" (both allow null)

[Jan Marti]

Hi there

If identify_hash != expected_hash, the trigger should deny the update.

I tried EVERYTHING, but there is not solution so it seems...

Major question: Is that possible with MySQL?

I get A LOT of strange error messages like "table does not exist in field list"

Current code is that:


SET SQL_NOTES = 0;

USE pf_server;

DROP TRIGGER IF EXISTS expected_hash_trigger;

DELIMITER $$
CREATE TRIGGER expected_hash_trigger
BEFORE UPDATE ON clientdb_mapping
FOR EACH ROW

BEGIN

IF (new.identify_hash = clientdb_mapping.expected_hash) THEN
-- UPDATE clientdb_mapping SET identify_hash = clientdb_mapping.expected_hash;
DELETE FROM pi_hash_migration_mapping;
END IF;

END $$

DELIMITER ;


SET SQL_NOTES = 1;