将三个计数查询合并为一个结果

Question

边学边学，但已经到了自我成长的极限。我希望将以下三个查询显示在一个查询中。但是我迷失在连接和联合的术语中。

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

这肯定会让人感到困惑。当您想将结果（或表格）连接在一起时，可以这样想：

如果您希望结果在同一行中，则需要 JOIN
如果您希望结果相互堆叠，则需要 UNION

在您的情况下，您希望它们并排放置，因此您必须将所有这些连接在一起。

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

我已经从每个子查询中删除了 ORDER BY 子句，因为您不能在子查询中执行 ORDER BY。我还从 GROUP BY 子句中删除了与 COUNT() 聚合的字段，因为如果您想计算它们，将它们放在那里没有多大意义。出于某种原因，MySQL 允许你做这样时髦的事情，即使它是荒谬的，如果你试图 GROUP BY 在你已经在 SELECT 中聚合的字段上，大多数 RDBMS 都会抛出错误条款。

Answer 2

也许使用相关子查询对您有用？

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：评论中要求的附加解决方案：

;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

Combine Three Count Queries to One Result

sql

count