Question

我可以有效地进行简单的连接，但是我面对以下复杂的SQL语句来加入第3个表以在结果中显示HostName。

我想添加切换表中存在的列HostName（SwitchID是主键，HostName是列）。

目前的陈述是：

SELECT  SwitchID, SUM(score)

我需要通过加入switch表在结果中显示SwitchID, HostName, SUM(score)。

我尝试了许多变化，但无法使其发挥作用。

SELECT SwitchID
,      SUM(score)
FROM   ( SELECT SwitchID
         ,      CallStackDepth * COUNT(*) AS score
         FROM   huntandpagingfeatures
         JOIN   huntgroupmembers
         ON     huntgroupmembers.HuntGroupDN = huntandpagingfeatures.ListDN
         WHERE  IsHuntGroup = 1
         GROUP
         BY     SwitchID
         ,      ListDN
         UNION
         ALL
         SELECT IF( ucw.currentportid IS NOT NULL
                  , ucw.currentswitchid
                  , ucw.homeswitchid
                  )
                AS SwitchID
         ,      count(*) / 2 AS score
         FROM   userprogbuttons AS upb
         INNER
         JOIN   usercurrentswitch AS ucw
         ON     upb.userdn = ucw.userdn
         WHERE  upb.functionid = 30
         GROUP
         BY     SwitchID
       ) AS t
GROUP
BY     SwitchID

Answer 1

SELECT t.SwitchID, SUM(score), s.HostName
FROM   ( SELECT SwitchID
     ,      CallStackDepth * COUNT(*) AS score
     FROM   huntandpagingfeatures
     JOIN   huntgroupmembers
     ON     huntgroupmembers.HuntGroupDN = huntandpagingfeatures.ListDN
     WHERE  IsHuntGroup = 1
     GROUP
     BY     SwitchID
     ,      ListDN
     UNION
     ALL
     SELECT IF( ucw.currentportid IS NOT NULL
              , ucw.currentswitchid
              , ucw.homeswitchid
              )
            AS SwitchID
     ,      count(*) / 2 AS score
     FROM   userprogbuttons AS upb
     INNER
     JOIN   usercurrentswitch AS ucw
     ON     upb.userdn = ucw.userdn
     WHERE  upb.functionid = 30
     GROUP
     BY     SwitchID
    ) AS t
JOIN switches s ON t.SwitchID = s.SwitchID
GROUP BY t.SwitchID, s.HostName

Answer 2

为简洁省略了子查询：

select
    SwitchID,
    HostName,
    sum(Score)
from
    ( ... ) as t
    join
    switches s on t.SwitchID = s.SwitchID
group by
    SwitchID,
    HostName

只需将HostName添加到group by并完成。

Answer 3

您可以按HostName分组以及切换ID：

SELECT SwitchID, SUM(score), HostName
--- skipping most of query for simplicity
    ) AS t
INNER JOIN Switches ON Switches.SwitchID = t.SwitchID
GROUP BY t.SwitchID, Switches.HostName

您还可以使用列列表中的子选择来返回主机名：

SELECT SwitchID, SUM(score),
    (SELECT HostName FROM Switches WHERE Switches.SwitchID = t.SwitchID) AS HostName

如何将第3个表连接到具有2个连接表的先前SQL语句？

3 个答案: