Question

我有两个选择查询，我试图对NULL作为列执行UNION。它仅对一个选择查询有效，但对其他查询则无效。请帮助

我正在计算B＆C类型的ID的总和1234，并在ID的最终选择查询中对其进行分组，并对FTN类型的相同ID的总和执行并集操作。

这意味着B＆C选择查询将始终具有“ Case”值，并且不是G。，而FTN将具有G值，并且没有Case 。

联合查询的问题是，它为B＆C生成正确的结果 C，但在FTN选择查询中对G显示NULL。我该如何解决？

这是我的查询

select [ID],sum([case2018])  as [Case18] , NULL AS [G18]  from 
    (SELECT [ID], [ID Was], SUM([Cases]) AS [Case2018], NULL AS [G2018] FROM TblX
    WHERE [Package Type]='B&C' and [Year]=2018 and  [ID]= 1234 
    GROUP BY [ID], [ID Was]) 
GROUP BY [ID]

union

select [ID], NULL AS [Case18] , sum([G2018]) as [G18]  from 
    (SELECT [ID], [ID Was], SUM([G]) AS G18 ,NULL as [Case2018] FROM TblX
    WHERE [Package Type]='FTN' and [Year]=2018 and [ID]= 1234 
    GROUP BY [ID], [ID Was]) 
GROUP BY [ID]

Answer 1

第二个查询不起作用，因为内部查询未选择名为[G2018]的字段。

我认为查询的嵌套不是必需的。我想您需要以下条件：

SELECT [ID], SUM([Cases]) AS [Case18], NULL AS [G18] 
FROM TblX 
WHERE [Package Type]='B&C' AND [Year]=2018 AND [ID]=1234 
GROUP BY [ID]
UNION
SELECT [ID], NULL AS [Case18] , SUM([G]) AS [G18]
FROM TblX 
WHERE [Package Type]='FTN' AND [Year]=2018 AND [ID]=1234 
GROUP BY [ID]

再仔细一点看，下面的单个SELECT不会产生预期的结果吗？

SELECT [ID], [Package Type], SUM([Cases]) AS [Case18], SUM([G]) AS [G18]
FROM TblX 
WHERE [Package Type] In ('B&C', 'FTN') AND [Year]=2018 AND [ID]=1234 
GROUP BY [ID], [Package Type]

Answer 2

我使用的站点是http://www.dpriver.com/pp/sqlformat.htm免费的在线sql格式化工具，可立即美化SQL Server，Oracle，DB2，MySQL，Sybase和Access的sql代码。这给了我可读的SQL。

为了进行分析，我然后在excel中将B＆C与FTN并排粘贴并发现了错误。然后我重新排列了FTN中的一些项目，并将拼写更改为G2018

               NULL     AS [Case2018],
               Sum([g]) AS [G2018]

SELECT [id],
       Sum([case2018]) AS [Case18],
       NULL            AS [G18]
FROM   (SELECT [id],
               [id was],
               Sum([cases]) AS [Case2018],
               NULL         AS [G2018]
        FROM   tblx
        WHERE  [package type] = 'B&C'
               AND [year] = 2018
               AND [id] = 1234
        GROUP  BY [id],
                  [id was])
GROUP  BY [id]
UNION
SELECT [id],
       NULL         AS [Case18],
       Sum([g2018]) AS [G18]
FROM   (SELECT [id],
               [id was],
               NULL     AS [Case2018],
               Sum([g]) AS [G2018]
        FROM   tblx
        WHERE  [package type] = 'FTN'
               AND [year] = 2018
               AND [id] = 1234
        GROUP  BY [id],
                  [id was])
GROUP  BY [id]

带有NULL列的Access Union不起作用

2 个答案: