Question

我想计算左连接mysql的条目，但我总是出错

SELECT g.uid,g.datei, u.id, u.avatar, u.avatarapproved, a.points, COUNT (g.uid) as hits
FROM jos_findme_gallery as g 
LEFT JOIN jos_findme as u ON g.uid= u.user_id 
LEFT JOIN jos_alpha_userpoints as a ON g.uid= a.userid 
WHERE u.avatar IS NOT NULL
ORDER BY g.uid asc

功能db1140411-dualda.COUNT不存在。检查参考手册中的“功能名称解析和解决方案”部分

任何想法？

Answer 1

在使用聚合函数时，应使用GROUP BY，但由于COUNT和(之间的空格，您会收到此特定错误。

From the MySQL Docs:

要求函数调用没有空格名称和括号之间仅适用于内置函数有特殊考虑的功能。 COUNT就是这样一个名字。

要解决这个问题，请摆脱空间...并将GROUP BY投入到显式：

SELECT 
  g.uid,
  g.datei, 
  u.id, 
  u.avatar, 
  u.avatarapproved, 
  a.points, 
  COUNT(g.uid) as hits
FROM jos_findme_gallery as g 
LEFT JOIN jos_findme as u ON g.uid= u.user_id 
LEFT JOIN jos_alpha_userpoints as a ON g.uid= a.userid 
WHERE u.avatar IS NOT NULL
GROUP BY 
  g.uid,
  g.datei, 
  u.id, 
  u.avatar, 
  u.avatarapproved, 
  a.points
ORDER BY g.uid asc

Answer 2

你需要分组。 COUNT是一个聚合函数。

SELECT g.uid,g.datei, u.id, u.avatar, u.avatarapproved, a.points, COUNT(1) as hits
...
GROUP BY g.uid
ORDER BY ...

另外，为什么你有2个左连接？您想要从哪两个连接表计算行数？

Answer 3

我认为在其他例子中我们可以看到计数和计数之间没有空格。

Answer 4

试试这个：

SELECT g.uid, g.datei, u.id, u.avatar, u.avatarapproved, a.points, COUNT(g.uid) AS hits
FROM jos_findme_gallery AS g 
LEFT JOIN jos_findme AS u ON g.uid= u.user_id 
LEFT JOIN jos_alpha_userpoints AS a ON g.uid= a.userid 
WHERE u.avatar IS NOT NULL
GROUP BY u.id
ORDER BY g.uid ASC

LEFT JOIN与COUNT获取错误

4 个答案: