mysql - 触发器未按预期工作

Question

我尝试在 mysql 数据库上执行触发器。命令执行成功，但触发器不起作用。

DELIMITER #

CREATE TRIGGER generate_coupon AFTER INSERT ON order
FOR EACH ROW
BEGIN

DECLARE userid, couponvalue INT;
DECLARE couponcode VARCHAR;
SELECT idUser INTO userid FROM indication WHERE email = NEW.email;
SET couponvalue = 20;
SET couponcode = 'abc123';

INSERT INTO coupon(idUser,idOrder,couponvalue,couponcode) values(userid, NEW.id, couponvalue, couponcode);

END# 

DELIMITER ;

Answer 1

我怀疑您的问题是由变量之间的冲突couponvalue以及couponcode表中的同名列引起的coupon。如Local Variable Scope and Resolution中所述：

局部变量不应与表列同名。

您可以将触发器简化为以下内容，这样可以完全避免此问题：

CREATE TRIGGER generate_coupon AFTER INSERT ON order FOR EACH ROW
  INSERT INTO coupon
    (idUser, idOrder, couponvalue, couponcode)
  SELECT idUser, NEW.id, 20, 'abc123'
  FROM   indication
  WHERE  email = NEW.email
;