ms-access - MS Access 错误 :the number of columns in the two selected tables does not match

Question

我在 MS Access 查询中遇到此错误:The number of columns in the two selected tables or queries of a union query do not match.
列数完全匹配，当我运行 UNION 查询时，一次选择任意 2 个集合，它工作正常。当我在查询中包含超过 2 个选择时，它会显示此错误。

SELECT  "Applied" as Application_Status, Count(*) AS [CountOfApplication Status]
FROM [EDB Applicants - ALL]
WHERE [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]>Date()-366

UNION

SELECT  "Hold" as Application_Status, Count(*) AS [CountOfApplication Status]
FROM [EDB Applicants - ALL]
WHERE [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]<=Date()-366 And [EDB Applicants - ALL].[Application Status]="Hold"

UNION

SELECT  "Withdraw" as Application_Status, Count(*) AS [CountOfApplication Status]
FROM [EDB Applicants - ALL]
WHERE [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Date of Enrollment Change]<=Date()-366 And [EDB Applicants - ALL].[Application Status] In ("Declined","Withdrew Application","Withdrew After Enrollment")

Answer 1

我不知道您的原始问题的原因，但您可以重写您的查询以消除联合:

select Application_Status, COUNT(*)
from (select (case when  [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]>Date()-366
                   then 'Applied'
                   when [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]<=Date()-366 And [EDB Applicants - ALL].[Application Status]="Hold"
                   then 'Hold'
                   when [EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Date of Enrollment Change]<=Date()-366 And [EDB Applicants - ALL].[Application Status] In ("Declined","Withdrew Application","Withdrew After Enrollment")
                   then 'Withdraw'
              end) as Application_Status, [EDB Applicants - ALL].*
      from [EDB Applicants - ALL]
     ) t
where Application_Status is not null
group by Application_Status

没错，在 MS Access 中你必须使用 IIF()，但同样的想法也适用:

select Application_Status, COUNT(*)
from (select iif([EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]>Date()-366,
                  'Applied',
                  iif([EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Dec Date]<=Date()-366 And [EDB Applicants - ALL].[Application Status]="Hold",
                       'Hold',
                       iif([EDB Applicants - ALL].[Application Year].Value Like "2012" And [EDB Applicants - ALL].[Application Date]<=Date()-366 And [EDB Applicants - ALL].[Date of Enrollment Change]<=Date()-366 And [EDB Applicants - ALL].[Application Status] In ("Declined","Withdrew Application","Withdrew After Enrollment")
                        'Withdraw', '')))) as Application_Status, [EDB Applicants - ALL].*
      from [EDB Applicants - ALL]
     ) t
where Application_Status <> ''
group by Application_Status