Coldfusion計數案例錯誤取決於數據源

Question

我正在使用Coldfusion使用COUNT CASE語句從數據庫中檢索一些值。

下面的SQL與SQL Server數據源完美地兼容：

<cfquery name="getData" datasource="cfTSP1_Dev">
  SELECT  SiteFK,
      Scheme,
      COUNT(case when DrawingTypeFK = 'Civil' then 1 else null end) as CCount,
      COUNT(case when DrawingTypeFK = 'Mechanical' then 1 else null end) as MCount,
      COUNT(case when DrawingTypeFK = 'Electrical' then 1 else null end) as ECount,
      COUNT(case when DrawingTypeFK = 'P & ID' then 1 else null end) as PCount,
      COUNT(case when DrawingTypeFK = 'Zoning' then 1 else null end) as ZCount
  FROM     Drawings.tblDrawingsData
  where     SiteFK = 'MYSITE'
  group by  SiteFK,Scheme
  order by Scheme

但是當我更改查詢以指向訪問數據庫中完全相同的表時，會收到錯誤消息：

<cfquery name="getData" datasource="drawingsLink">
  SELECT  SiteFK,
      Scheme,
      COUNT(case when DrawingTypeFK = 'Civil' then 1 else null end) as CCount,
      COUNT(case when DrawingTypeFK = 'Mechanical' then 1 else null end) as MCount,
      COUNT(case when DrawingTypeFK = 'Electrical' then 1 else null end) as ECount,
      COUNT(case when DrawingTypeFK = 'P & ID' then 1 else null end) as PCount,
      COUNT(case when DrawingTypeFK = 'Zoning' then 1 else null end) as ZCount
  FROM     tblDrawingsData
  where     SiteFK = 'MYSITE'
  group by  SiteFK,Scheme
  order by Scheme

錯誤是這樣的：

[Macromedia] [SequeLink JDBC驅動程序] [ODBC套接字] [Microsoft] [ODBC Microsoft Access驅動程序]語法錯誤（缺少運算符）在查詢表達式“ COUNT（在DrawingTypeFK ='Civil'時為1，否則為null結束）。

有什么想法嗎？ 我唯一的理論是它的訪問驅動程序，但我使用此數據源的其他查詢（無Count Case）都很好。

干杯尼爾

Answer 1

Access的數據庫引擎不支持CASE ... WHEN ，因此您需要重寫查詢。 您可以在Access SQL中使用IIf()近似CASE ... WHEN 。

SELECT  SiteFK,
  Scheme,
  Count(IIf(DrawingTypeFK = 'Civil', 1, null)) as CCount

Count()僅計算非Null值，因此應該給您我認為想要的東西。 但是，如果要使用Sum() ，如注釋中所建議，這也應該起作用：

Sum(IIf(DrawingTypeFK = 'Civil', 1, 0)) as CCount

Answer 2

我尚未測試此代碼，並且我想它的效率將比您的代碼低得多，但它應可在MS Access中使用。 如果您的代碼可以在所需的任何地方工作，那么我認為它比下面的代碼更好。

SELECT
        SiteFK,
        Scheme,
        (
            SELECT  count(*)
            FROM    Drawings.tblDrawingsData Civil
            WHERE   Civil.Scheme = tblDrawingsData.Scheme
                AND Civil.DrawingTypeFK = 'Civil'
        ) AS CCount,
        (
            SELECT  count(*)
            FROM    Drawings.tblDrawingsData Civil
            WHERE   Civil.Scheme = tblDrawingsData.Scheme
                AND Civil.DrawingTypeFK = 'Mechanical'
        ) AS MCount,
        (
            SELECT  count(*)
            FROM    Drawings.tblDrawingsData Civil
            WHERE   Civil.Scheme = tblDrawingsData.Scheme
                AND Civil.DrawingTypeFK = 'Electrical'
        ) AS ECount,
        (
            SELECT  count(*)
            FROM    Drawings.tblDrawingsData Civil
            WHERE   Civil.Scheme = tblDrawingsData.Scheme
                AND Civil.DrawingTypeFK = 'P & ID'
        ) AS PCount,
        (
            SELECT  count(*)
            FROM    Drawings.tblDrawingsData Civil
            WHERE   Civil.Scheme = tblDrawingsData.Scheme
                AND Civil.DrawingTypeFK = 'Zoning'
        ) AS ZCount
  FROM      Drawings.tblDrawingsData
  WHERE     SiteFK = 'MYSITE'
  GROUP BY  SiteFK, Scheme
  ORDER BY  Scheme

這是一個相關的子查詢，因此它可能非常慢。 買家當心。