What is the issue with this trigger (for the right syntax to use near '' )

问题

Please I did this trigger to update table rating after each insert when 2 columns (id_prof,id_etud) inserted are already in the table but it gives mi this error

> #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 6

The trigger :

CREATE TRIGGER Before_Insert_Rate
BEFORE INSERT ON rating
FOR EACH ROW
BEGIN
  IF (EXISTS(SELECT * FROM rating WHERE id_prof=NEW.id_prof and id_etud = NEW.id_etud)) THEN
    UPDATE `rating` SET `rate` = NEW.rate WHERE `id_prof` = NEW.id_prof and `id_etud` = NEW.id_etud; 
    ELSE INSERT INTO rating VALUES (NEW.idprof,New.rate,New.id_etud);
  END IF
END
DELIMITER ;

回答1:

You must set the DELIMITER before. Change it to:

DELIMITER //
CREATE TRIGGER Before_Insert_Rate
BEFORE INSERT ON rating
FOR EACH ROW
BEGIN
  IF (EXISTS(SELECT * FROM rating WHERE id_prof=NEW.id_prof and id_etud = NEW.id_etud)) THEN
    UPDATE `rating` SET `rate` = NEW.rate WHERE `id_prof` = NEW.id_prof and `id_etud` = NEW.id_etud; 
    ELSE INSERT INTO rating VALUES (NEW.idprof,New.rate,New.id_etud);
  END IF
  END; //

DELIMITER ;

回答2:

from the official reference manual.

A trigger can access both old and new data in its own table. A trigger can also affect other tables, but 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.

This means no query on table X can INSERT, UPDATE, or DELETE from table X; it also means that if a trigger on table X modifies table Y, it will fail for any query using both table X and Y that "triggers" it.

Example: UPDATE x INNER JOIN y ON x.id = y.id SET x.something = 1, y.something = 2 will cause a BEFORE UPDATE ON x trigger (that updates, inserts, or deletes from y) to fail.

回答3:

I solved it using ON DUPLICATE KEY on a query instead of trigger

CREATE TABLE `rating` (
  `id_prof` int(11) NOT NULL,
  `rate` float NOT NULL,
  `id_etud` int(11) NOT NULL,
UNIQUE (id_prof,id_etud)
)

the query :

INSERT INTO rating (id_prof,rate,id_etud) VALUES (1,2,5)
ON DUPLICATE KEY UPDATE rate=2

来源：https://stackoverflow.com/questions/48233990/what-is-the-issue-with-this-trigger-for-the-right-syntax-to-use-near

标签

mysql

triggers