[英]The used SELECT statements have a different number of columns (REDUX!!)
那里还有另一个与此类似的问题,但似乎没有回答我的问题。
我的问题是:为什么我会找回此错误ERROR 1222 (21000): The used SELECT statements have a different number of columns
与以下SQL ERROR 1222 (21000): The used SELECT statements have a different number of columns
SELECT * FROM friends
LEFT JOIN users AS u1 ON users.uid = friends.fid1
LEFT JOIN users AS u2 ON users.uid = friends.fid2
WHERE (friends.fid1 = 1) AND (friends.fid2 > 1)
UNION SELECT fid2 FROM friends
WHERE (friends.fid2 = 1) AND (friends.fid1 < 1)
ORDER BY RAND()
LIMIT 6;
这里的users
:
+------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+---------------+------+-----+---------+----------------+
| uid | int(11) | NO | PRI | NULL | auto_increment |
| first_name | varchar(50) | NO | | NULL | |
| last_name | varchar(50) | NO | | NULL | |
| email | varchar(128) | NO | UNI | NULL | |
| mid | varchar(40) | NO | | NULL | |
| active | enum('N','Y') | NO | | NULL | |
| password | varchar(64) | NO | | NULL | |
| sex | enum('M','F') | YES | | NULL | |
| created | datetime | YES | | NULL | |
| last_login | datetime | YES | | NULL | |
| pro | enum('N','Y') | NO | | NULL | |
+------------+---------------+------+-----+---------+----------------+
这是friends
:
+---------------+--------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------------------------------+------+-----+---------+----------------+
| friendship_id | int(11) | NO | MUL | NULL | auto_increment |
| fid1 | int(11) | NO | PRI | NULL | |
| fid2 | int(11) | NO | PRI | NULL | |
| status | enum('pending','accepted','ignored') | NO | | NULL | |
+---------------+--------------------------------------+------+-----+---------+----------------+
如果您也想对这里发生的任何疯狂事情提供任何反馈,请随时这样做。 我会结成小块。
UNION( UNION
和UNION ALL
)要求所有被UNION ALL
的查询都具有:
您的查询有:
SELECT f.*, u1.*, u2.* ...
UNION
SELECT fid2 FROM friends
我最简单的重写是:
SELECT f.*, u.*
FROM FRIENDS AS f
JOIN USERS AS u ON u.uid = f.fid2
WHERE f.fid1 = 1
AND f.fid2 > 1
UNION
SELECT f.*, u.*
FROM FRIENDS AS f
JOIN USERS AS u ON u.uid = f.fid1
WHERE f.fid2 = 1
AND f.fid1 < 1
ORDER BY RAND()
LIMIT 6;
您已经两次两次加入USERS
表,但似乎没有使用该信息。
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