添加触发器的正确​​语法

Question

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中添加触发器时，我收到错误：

#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代替*，我会收到错误：

#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

请告诉我如何正确添加触发器？

Answer 1

听起来令人难以置信，在mysql中，count和(*)之间没有空格：

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

在你的情况下，它在第二个子查询中。将其更改为：

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

---

这同样适用于cast(...)，这是语法错误：cast (col as unsigned)（请注意cast和(之间的空格）。我可以告诉你，我浪费了大约一个小时的时间来捕捉这颗小宝石。

---

编辑;

另一个错误可能是由于没有更改分隔符，如果在过程中有分号，则需要使用分隔符：

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 ;

Answer 2

试一试：

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