Question

我正在学习，但我已经达到了自我成长的极限。我希望下面有三个查询，显示在一个查询中。但我迷失在联合和工会的术语中。

SELECT    DID.display as "DisplayID",
          COUNT(AltID.REFID) as "C_AltIDs"
FROM      DID,
          AltID
WHERE     DID.REFID = AltID.REFID
GROUP BY  AltID.REFID, DID.display 
ORDER BY  COUNT(AltID.REFID) desc;


SELECT    DID.display as "DisplayID",
          COUNT(address.REFID) as "C_AltAddresses"
FROM      DID,
          address
WHERE     DID.REFID = address.REFID
GROUP BY  address.REFID, DID.display 
ORDER BY  COUNT(address.REFID) desc;


SELECT    DID.display as "DisplayID",
          COUNT(name.REFID) as "C_AltNames"
FROM      DID,
          name
WHERE     DID.REFID = name.REFID
GROUP BY  name.REFID, DID.display 
ORDER BY  COUNT(name.REFID) desc;



**Desired end result**
|DisplayID|AltIDs|AltAddresses|AltNames|
    01       32        32         2
    02        2        12         4

Answer 1

肯定会让人感到困惑。如果要将结果（或表）连接在一起，请以这种方式考虑：

如果您希望结果位于同一行，那么您需要加入
如果您希望将结果叠加在一起，那么您需要一个UNION

在你的情况下，你想要并排，所以你必须将所有这些加在一起。

SELECT
    t1.display,
    t1.C_AltIDs,
    t2.C_AltAddresses,
    t3.C_AltNames
FROM
    (
        SELECT    DID.display as "DisplayID",
              COUNT(AltID.REFID) as "C_AltIDs"
        FROM      DID,
              AltID
        WHERE     DID.REFID = AltID.REFID
        GROUP BY  DID.display 
    ) t1

    LEFT OUTER JOIN
    (

        SELECT    DID.display as "DisplayID",
              COUNT(address.REFID) as "C_AltAddresses"
        FROM      DID,
              address
        WHERE     DID.REFID = address.REFID
        GROUP BY  DID.display 
    ) t2 ON
        t1.Display = t2.Display

    LEFT OUTER JOIN
    (
        SELECT    DID.display as "DisplayID",
              COUNT(name.REFID) as "C_AltNames"
        FROM      DID,
              name
        WHERE     DID.REFID = name.REFID
        GROUP BY  DID.display 
    ) t3 ON
        t1.Display = t3.Display

我已从每个子查询中删除了ORDER BY子句，因为您无法在子查询中执行ORDER BY。我还从COUNT()条款中删除了与GROUP BY汇总的字段，因为如果您想要计算它们，那么将它们放在那里是没有意义的。出于某种原因，MySQL允许您使用类似时髦的东西，即使它是荒谬的，如果您在GROUP BY已经聚合的字段上尝试SELECT，大多数RDBMS都会引发错误子句。

Answer 2

使用相关子查询可能对你有用吗？

SELECT    
  DID.display as "DisplayID",
  (SELECT COUNT(AltID.REFID) FROM AltID WHERE REFID = DID.REFID) as "C_AltIDs",
  (SELECT COUNT(address.REFID) FROM address WHERE REFID = DID.REFID) as "C_AltAddresses",
  (SELECT COUNT(name.REFID) FROM name WHERE REFID = DID.REFID) as "C_AltNames" 
FROM DID
ORDER BY display

编辑：评论中要求提供的其他解决方案：

;WITH x AS (
  SELECT    
    DID.display as "DisplayID",
    (SELECT COUNT(AltID.REFID) FROM AltID WHERE REFID = DID.REFID) as "C_AltIDs",
    (SELECT COUNT(address.REFID) FROM address WHERE REFID = DID.REFID) as "C_AltAddresses",
    (SELECT COUNT(name.REFID) FROM name WHERE REFID = DID.REFID) as "C_AltNames" 
  FROM DID
) 

SELECT *, C_AltIDs+C_AltAddresses+C_AltNames AS SumOfCounts 
FROM x

将三个计数查询合并为一个结果

2 个答案: