Question

我有两张桌子：

用户：{id，name，studentid，overall_score} userbadges：{id，badge_id，user_id，level，score}

用户可以拥有多个徽章。

我希望将overall_score更新本身作为userbadges中所有分数的总和，其中user_id匹配用户表中的id。

这可以作为触发器完成吗？

我有一个mysql语句在php中工作，它只显示总分，但实际上并没有更新任何内容。

PHP：

$userscore = mysqli_query($connection,"

SELECT users.studentid
     , SUM(score) AS TotalItemsOrdered
  FROM userbadges ub
 INNER 
  JOIN users 
    ON users.id = ub.user_id
  WHERE studentid = $_SESSION['studentid']
")  or die(mysqli_error($connection));


  while ($data = mysqli_fetch_array($userscore)) {

echo $data['TotalItemsOrdered'];

Answer 1

尝试此查询（已编辑）：

 update USERS u 
 set u.overall_score = 
 ( select sum(b.score) from USERBADGES b 
   where b.user_id=u.id  ) ;

现在如果您想每天自动运行此查询，请使用MySQL调度程序，如下所示：

 DELIMITER $$
 CREATE EVENT update_users_table
 ON SCHEDULE EVERY 1 DAY
 STARTS '2015-05-27 00:00:00'
 DO 
 BEGIN
    update USERS u 
    set u.overall_score = 
    ( select sum(b.score) from USERBADGES b 
     where b.user_id=u.id  ) ;
 END$$    
 DELIMITER ;

如果您想在更新后自动运行此查询，请转到触发器：

 DELIMITER $$
 CREATE TRIGGER update_users_trigger AFTER UPDATE ON USERBADGES
 FOR EACH ROW
 BEGIN
    IF NEW.score <> OLD.score THEN  
        update USERS u 
        set u.overall_score = 
       ( select sum(b.score) from USERBADGES b 
         where b.user_id=u.id  ) ;
    END IF;
 END$$
 DELIMITER ;

Answer 2

Sagar的触发器是一种解决方案。但是，这个版本效率更高：

 DELIMITER $$
 CREATE TRIGGER update_users_trigger AFTER UPDATE ON USERBADGES
 FOR EACH ROW
 BEGIN
    IF NEW.score <> OLD.score THEN  
        update USERS u 
            set u.overall_score = u.overall_score  + new.score - old.score                          
            where u.user_id = new.user_id;
    END IF;
 END$$

或者，如果您希望完全重新计算：

 DELIMITER $$
 CREATE TRIGGER update_users_trigger AFTER UPDATE ON USERBADGES
 FOR EACH ROW
 BEGIN
    IF NEW.score <> OLD.score THEN  
        update USERS u 
            set u.overall_score = (select sum(b.score)
                                   from USERBADGES b 
                                   where b.user_id = u.id
                                  )
            where u.user_id = new.user_id
------------^
    END IF;
 END$$
 DELIMITER ;

为了提高性能，您需要userbadges(user_id, score)上的索引。

根据其他人的总和更新表中的字段

2 个答案: