Question

我有两个表'testing1'，其中包含字段'firstname'和'lastname'。另一个表'testing2'，字段'firstname'。

因此触发器首先检查'testing2'表中是否存在'NEW.firstname'。如果确实如此，则它不执行INSERT查询但如果它不存在则执行INSERT查询并在'testing2'表中添加'NEW.firstname'。

这是我创建的触发器......但我在IF循环中遇到错误......

DELIMITER $$;
CREATE TRIGGER testRef AFTER INSERT ON testing1
FOR EACH ROW
BEGIN
DECLARE rowCount INTEGER;
SET @rowCount := ( SELECT COUNT(firstname) FROM testing2 WHERE testing2.firstname =        NEW.firstname );
IF (rowCount) 
INSERT INTO testing2 (firstname) VALUES (NEW.firstname);
END $$

我无法弄清楚我在哪里弄错了......有任何帮助吗？

Answer 1

尝试

DELIMITER $$;
CREATE TRIGGER testRef AFTER INSERT ON testing1
FOR EACH ROW
BEGIN
DECLARE rowCount INTEGER;
SET @rowCount := ( SELECT COUNT(firstname) FROM testing2 WHERE testing2.firstname =        NEW.firstname );
IF (rowCount) THEN
INSERT INTO testing2 (firstname) VALUES (NEW.firstname);
END IF;
END$$
DELIMITER ;

但也许你应该使用IF（rowCount）＆gt; 0

Answer 2

这对我有用：

DELIMITER //
CREATE TRIGGER testRef AFTER INSERT ON testing1
FOR EACH ROW
BEGIN
DECLARE rowCount INTEGER;
SELECT COUNT(firstname) FROM testing2 WHERE testing2.firstname = NEW.firstname INTO rowCount;
IF rowCount = 0 THEN
INSERT INTO testing2 (firstname) VALUES (NEW.firstname);
END IF;
END //
DELIMITER ;

在MySQL中执行查询触发器无法正常工作

2 个答案: