Sql 帮助限制内部联接
我需要帮助限制内部连接 表格:Sql 帮助限制内部联接,sql,mysql,inner-join,Sql,Mysql,Inner Join,我需要帮助限制内部连接 表格: uid 3 3 3 3 7 47 47 47 47 47 47 47 47 47 47 uid 3 3 3 3 7 47 47 47 47 47 用户: 液体 左 活跃的 文件: uid 3 3 3 3 7 47 47 47 47 47 47 47 47 47 47 uid 3 3 3 3 7 47 47 47 47 47 氢火焰离子化检测器 uid=fid 结果: uid 3 3 3 3 7 47 47 47 47 47 47 47 47
uid
3
3
3
3
7
47
47
47
47
47
47
47
47
47
47
uid
3
3
3
3
7
47
47
47
47
47
用户:
- 液体
- 左
- 活跃的
文件:
uid
3
3
3
3
7
47
47
47
47
47
47
47
47
47
47
uid
3
3
3
3
7
47
47
47
47
47
- 氢火焰离子化检测器
uid=fid
结果:
uid
3
3
3
3
7
47
47
47
47
47
47
47
47
47
47
uid
3
3
3
3
7
47
47
47
47
47
我需要将内部联接限制为5。所以“uid”不会出现超过5次。比如:
uid
3
3
3
3
7
47
47
47
47
47
47
47
47
47
47
uid
3
3
3
3
7
47
47
47
47
47
更新:
uid
3
3
3
3
7
47
47
47
47
47
47
47
47
47
47
uid
3
3
3
3
7
47
47
47
47
47
下面是php代码
$res = do_sqlquery("SELECT uid FROM users as u INNER JOIN files as x ON u.fid=x.fid WHERE u.left = '0' AND u.active='1'");
if (mysql_num_rows($res) > 0)
{
while ($arr = mysql_fetch_assoc($res))
{
$x=$arr["uid"];
quickQuery("UPDATE users SET pots = pots+".$GLOBALS["bui"]."*".$cleaint."/900 WHERE id = '$x'");
}
}
在MySQL中:
SELECT CONCAT(`uid`, ":", MAX(5, COUNT(`fid`))) `uid_count`
FROM ...
GROUP BY `uid`
为您提供如下结果:
uid_count
3:4
7:1
47:5
例如,在PHP中,您可以在获取后拆分:
while (FALSE !== ($row = mysql_fetch_assoc($query))) {
($uid, $count) = split(':', $row['uid_count'], 2);
}
在MySQL中:
SELECT CONCAT(`uid`, ":", MAX(5, COUNT(`fid`))) `uid_count`
FROM ...
GROUP BY `uid`
为您提供如下结果:
uid_count
3:4
7:1
47:5
例如,在PHP中,您可以在获取后拆分:
while (FALSE !== ($row = mysql_fetch_assoc($query))) {
($uid, $count) = split(':', $row['uid_count'], 2);
}
仅MySQL解决方案,不使用PHP
SELECT uid
from (
SELECT u.uid, @r:= if(@u=u.uid,@r+1,1) r, @u:=u.uid
FROM users AS u
CROSS JOIN (select @u:=null) g
INNER JOIN files AS x ON u.uid = x.fid
WHERE u.`left` = '0'
AND u.active = '1'
ORDER BY u.uid ASC
) U
WHERE U.r <= 5
ORDER BY uid ASC
仅MySQL解决方案,不使用PHP
SELECT uid
from (
SELECT u.uid, @r:= if(@u=u.uid,@r+1,1) r, @u:=u.uid
FROM users AS u
CROSS JOIN (select @u:=null) g
INNER JOIN files AS x ON u.uid = x.fid
WHERE u.`left` = '0'
AND u.active = '1'
ORDER BY u.uid ASC
) U
WHERE U.r <= 5
ORDER BY uid ASC
谢谢,但没用。结果是不对的。我编辑了我的帖子,并添加了phpI just test you code on my localhost和“仅限MySQL的解决方案”结果不正确。“仅限不含MySQL变量的SQL”在我的localhost服务器版本:5.1.37上效果很好,但在我的站点服务器版本:5.0.91-community-log上,我收到错误#1054-在'field list'中未知列'u.uid'。user该版本可能区分大小写。将第一行更改为大写
选择U.uid
。否则,您是否更改了本地主机和站点服务器之间的任何表/别名?谢谢,但不起作用。结果是不对的。我编辑了我的帖子,并添加了phpI just test you code on my localhost和“仅限MySQL的解决方案”结果不正确。“仅限不含MySQL变量的SQL”在我的localhost服务器版本:5.1.37上效果很好,但在我的站点服务器版本:5.0.91-community-log上,我收到错误#1054-在'field list'中未知列'u.uid'。user该版本可能区分大小写。将第一行更改为大写选择U.uid
。否则,您是否更改了本地主机和站点服务器之间的任何表/别名?@Pablo Santa Cruz-MySQLclient@PabloSanta Cruz MySQL客户端