當我在回復表新增數據 我就會執行下列語句

觸發器在mysql的使用過DELIMITER $$開頭 END; $$ 結尾，注意 觸發的語句必須用；結尾

創建觸發器
DELIMITER $$
CREATE TRIGGER comment_Trigger1
AFTER INSERT ON reply
FOR EACH ROW
BEGIN
UPDATE COMMENT
SET replyid= (SELECT COUNT(*) FROM reply WHERE reply.commentid = new.commentid )
WHERE commentid=new.commentid;
END;
$$

DELIMITER $$
CREATE TRIGGER 觸發器名
BEFORE|AFTER DELETE|INSERT|UPDATE
ON 表名 FOR EACH ROW
BEGIN
觸發SQL代碼塊;
END;
$$

--觸發器刪除評論 回復清空

DELIMITER $$
CREATE TRIGGER commentDelete
BEFORE DELETE ON COMMENT
FOR EACH ROW
BEGIN
DELETE FROM reply WHERE old.commentid;
END;
$$

SHOW TRIGGERS --查看觸發器

DROP TRIGGER commentDelete --刪除觸發器

UPDATE COMMENT
SET replyid= (SELECT COUNT(*) FROM reply WHERE reply.commentid = new.commentid )
WHERE commentid=new.commentid;
END;
$$

DELIMITER $$
CREATE TRIGGER 觸發器名
BEFORE|AFTER DELETE|INSERT|UPDATE
ON 表名 FOR EACH ROW
BEGIN
觸發SQL代碼塊;
END;
$$

--觸發器刪除評論 回復清空

DELIMITER $$
CREATE TRIGGER commentDelete
BEFORE DELETE ON COMMENT
FOR EACH ROW
BEGIN
DELETE FROM reply WHERE  old.commentid;
END;
$$

SHOW TRIGGERS --查看觸發器

DROP TRIGGER commentDelete --刪除觸發器

總結

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