添加触发器的正确​​语法

Posted 2023-02-25

【中文标题】添加触发器的正确​​语法

【英文标题】：Right syntaxis for add trigger

【发布时间】：2014-02-10 15:06:03

【问题描述】：

代码：

# Triggers for table Likes->News

CREATE TRIGGER `TriggerUpdateNewsAfterInsertLikes` AFTER INSERT ON `Likes`
FOR EACH ROW
BEGIN 
UPDATE `News` SET 
`CountUpLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'up'),
`CountDownLikes` = (SELECT COUNT (*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'down'),
`CountFavorites` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `IsFavorite` = 'yes');
END;

当我想在 phpmyadmin 中添加它时，我得到了错误：

#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 '*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` 
AND `Type` = 'down'),
`CountFav' at line 8 

如果我使用id 而不是* 我会出错：

#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 '' at line 9

请告诉我如何正确添加触发器？

【参考方案1】：

听起来难以置信，在 mysql 中，count 和 (*) 之间不能有空格：

select count(*) -- OK
select count (*) -- syntax error!

在您的情况下，它位于第二个子查询中。将其更改为：

...
`CountDownLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'down'),
...

---

同样适用于cast(...)，这是一个语法错误：cast (col as unsigned)（注意cast和(之间的空格）。我可以告诉你，我浪费了大约一个小时来寻找那个小宝石。

---

编辑；

另一个错误可能是由于未更改分隔符，如果您在过程中有分号，则需要这样做：

DELIMITER //

CREATE TRIGGER `TriggerUpdateNewsAfterInsertLikes` AFTER INSERT ON `Likes`
FOR EACH ROW
BEGIN 
UPDATE `News` SET 
`CountUpLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'up'),
`CountDownLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'down'),
`CountFavorites` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `IsFavorite` = 'yes');
END;//

DELIMITER ;

【讨论】：

哦，抱歉，我没看到，我认为 * 或 '' 中的错误。非常感谢和抱歉。

现在我得到第二个错误（#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 '' at line 9 ）。请看代码pastebin.com/gSr70eci

【参考方案2】：

试试看：

DELIMITER //
CREATE TRIGGER `TriggerUpdateNewsAfterInsertLikes` AFTER INSERT ON `Likes`
FOR EACH ROW BEGIN
UPDATE `News` SET 
`CountUpLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'up'),
`CountDownLikes` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `Type` = 'down'),
`CountFavorites` = (SELECT COUNT(*) FROM `Likes` WHERE `NewsIdn` = NEW.`NewsIdn` AND `IsFavorite` = 'yes');
END