当其他表上没有更多行时，SQL 删除行

Question

我正在尝试在 phpmyadmin 上创建触发器。 一旦WAITING_ROOM 中没有更多行，我想从表NEXT_GAME 中删除所有行。

我尝试了以下解决方案：

CREATE TRIGGER delete_begin_date AFTER DELETE
ON NEXT_GAME FOR EACH ROW
BEGIN
    IF NOT EXISTS (SELECT * FROM WAITING_ROOM) THEN
        DELETE FROM NEXT_GAME;
    END IF;
END

我收到以下错误：

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 5

我做错了什么？

Answer 1

您需要一个特定的分隔符来告诉 MySQL 下一个 ; 不会结束 CREATE TRIGGER 语句。

DELIMITER $$
CREATE TRIGGER delete_begin_date AFTER DELETE
ON NEXT_GAME FOR EACH ROW
BEGIN
    IF NOT EXISTS (SELECT * FROM WAITING_ROOM) THEN
        DELETE FROM NEXT_GAME;
    END IF;
-- vv----------------------- Notice this
END$$
DELIMITER ; -- switch back to the regular ;