MySQL触发器：＃1064-您的SQL语法有误； 检查与您的MySQL服务器版本相对应的手册

Question

I have problems creating triggers in MySQL 5.1.73 This is de syntax:

DELIMITER $$
CREATE TRIGGER `discount2` 
BEFORE 
INSERT ON `order_item` 
FOR EACH ROW 
DECLARE alumno INT;
DECLARE profesor INT;
DECLARE dto decimal(10,2);
SET @alumno := (SELECT user_id from `order` where `order`.id = NEW.order_id)
SET @profesor := (SELECT id_profesor from user where user.id = @alumno)
SET @dto := (SELECT descuento from descuentos
join user on descuentos.id_profesor = user.id
join producto on producto.familia=descuentos.familia
where producto.id = NEW.product_id and user.id = @profesor)

SET.NEW.descuento = SELECT CAST((((@dto)*(NEW.pvp))/100) AS DECIMAL(10,2))
$$
DELIMITER ;

But there is some error...

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DECLARE alumno INT;
DECLARE profesor INT;
DECLARE dto decimal(10,2);
SET @alu' at line 5

Someone can help me, please? Thanks u

Answer 1

The syntax to create a BEFORE INSERT Trigger in MySQL is:

CREATE TRIGGER trigger_name
BEFORE INSERT
   ON table_name FOR EACH ROW

BEGIN

   -- variable declarations

   -- trigger code

END;

If you want to execute multiple statements in your trigger, you should use BEGIN and END .

The Reason for using DELIMITER $$ before and after the trigger declaration is to change the delimiter from ; (default) to $$ .

If you didn't change the DELIMITER , the first semicolon in your trigger code may be interpreted as the end of trigger declaration. Thus the code following may result in syntax errors.

DELIMITER $$
CREATE TRIGGER `discount2` 
BEFORE 
INSERT ON `order_stage` 
FOR EACH ROW 
BEGIN

   DECLARE alumno INT;
   DECLARE profesor INT;
   DECLARE dto decimal(10,2);
   SET alumno = (SELECT user_id from `order` where `order`.id = NEW.order_id);
   SET profesor = (SELECT id_profesor from user where user.id = alumno);
   SET dto = (SELECT descuento from descuentos
   join user on descuentos.id_profesor = user.id
   join producto on producto.familia=descuentos.familia
   where producto.id = NEW.product_id and user.id = profesor);

   SET NEW.descuento = (SELECT CAST((((dto)*(NEW.pvp))/100) AS DECIMAL(10,2)));
END;
$$
DELIMITER ;

Read More Here

Answer 2

Note this syntaxs but may not 'work'

drop trigger if exists discount2;

DELIMITER $$
CREATE TRIGGER `discount2` 
BEFORE 
INSERT ON `order_stage` 
FOR EACH ROW 
begin
DECLARE alumno INT;
DECLARE profesor INT;
DECLARE dto decimal(10,2);
SET alumno = (SELECT user_id from `order` where `order`.id = NEW.order_id);
SET profesor = (SELECT id_profesor from user where user.id = alumno);
SET dto = (SELECT descuento from descuentos
join user on descuentos.id_profesor = user.id
join producto on producto.familia=descuentos.familia
where producto.id = NEW.product_id and user.id = profesor);

SET NEW.descuento = (SELECT CAST((((dto)*(NEW.pvp))/100) AS DECIMAL(10,2)));
end $$
DELIMITER ;