Question

我在表B中与表C有着许多对称的关系。这就是说,

TableA       TableB           TableC
id | val     fkeyA | fkeyC    id | data

我祝愿表A的<代码>电子数据总和/代码”按与表C的关系分类。表A中的每一条目与表C至少有一个关系。例如,

TableA
1 | 25
2 | 30
3 | 50

TableB
1 | 1
1 | 2
2 | 1
2 | 2
2 | 3
3 | 1
3 | 2

should output

75
30

由于表1和第3行与表C有着相同的关系,但表A第2行与表C有着不同的关系。

我怎么能为这一点撰写一个文件吗?

Answer 1

SELECT    
   sum(tableA.val) as sumVal,    
   tableC.data  
FROM    
   tableA 
     inner join tableB ON tableA.id = tableB.fkeyA 
     INNER JOIN tableC ON tableB.fkeyC = tableC.id  
GROUP by tableC.data

edit Ah ha - I now see what you re getting at. Let me try again:

SELECT
   sum(val) as sumVal,
   tableCGroup
FROM
(

SELECT 
   tableA.val,
   (
      SELECT cast(tableB.fkeyC as varchar) +  ,  
      FROM tableB WHERE tableB.fKeyA = tableA.id
      ORDER BY tableB.fkeyC
      FOR XML PATH(  ) 
   ) as tableCGroup
FROM
   tableA


) tmp
GROUP BY
    tableCGroup

Answer 2

Hm, 可在MySQL中写成:

SELECT
    SUM(val) AS sumVal
FROM
    ( SELECT
          fkeyA
        , GROUP_CONCAT(fkeyC ORDER BY fkeyC) AS grpC
      FROM 
          TableB
      GROUP BY
          fkeyA
    ) AS g
  JOIN
    TableA a
      ON a.id = g.fkeyA
GROUP BY 
    grpC

Answer 3

SELECT sum(a.val) 
FROM  tablea a
INNER JOIN tableb b ON (b.fKeyA = a.id)
GROUP BY b.fKeyC

Answer 4

似乎需要制定一份关键清单,以便通过:

75 -> key list = "1 2"
30 -> key list = "1 2 3"

因为小组――CONCAT T-SQL没有:

WITH CTE ( Id, key_list )
          AS ( SELECT TableA.id, CAST(    AS VARCHAR(8000) )
                 FROM TableA 
                GROUP BY TableA.id
                UNION ALL
               SELECT TableA.id, CAST( key_list +     + str(TableB.id) AS VARCHAR(8000) )
                 FROM CTE c
                INNER JOIN TableA A
                   ON c.Id = A.id
                INNER join TableB B
                   ON B.Id = A.id
                WHERE A.id > c.id      --avoid infinite loop
              )
Select
   sum( val )
from 
   TableA inner join
   CTE on (tableA.id = CTE.id)
group by
   CTE.key_list

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