mysql - 让这个查询工作？

Question

嘿!，我有以下查询:

SELECT t1.pm_id 
  FROM fb_user_pms AS t1, 
       fb_user_pm_replies AS t2 
 WHERE (t1.pm_id = '{$pm_id}' 
   AND t1.profile_author = '{$username}' 
    OR t1.pm_author = '{$username}' 
   AND t1.pm_id = t2.pm_id 
   AND t2.pm_author = '{$username}' 
   AND COUNT(t2.reply_id) > 0) 
   AND t1.deleted = 0

但是，我遇到了分组错误 - 我猜测是由 AND COUNT(t2.reply_id) > 0 引起的？

如何纠正上述查询以使其正常工作。

希望有人能帮忙。

干杯!

Answer 1

聚合函数 COUNT 不能出现在 WHERE 子句中。您应该使用 GROUP BY 并将其放在 HAVING 子句中。

SELECT t1.pm_id
FROM fb_user_pms AS t1
JOIN fb_user_pm_replies AS t2 ON t1.pm_id = t2.pm_id
WHERE (
         (t1.pm_id = '{$pm_id}' AND t1.profile_author = '{$username}') OR
         (t1.pm_author = '{$username}' AND t2.pm_author = '{$username}')
      ) AND t1.deleted = 0
GROUP BY t1.pm_id
HAVING COUNT(t2.reply_id) > 0

如果 t2.reply_id 是 NOT NULL 列，那么您根本不需要 HAVING 子句。