Coldfusion计数案例错误取决于数据源

Question

我正在使用Coldfusion使用COUNT CASE语句从数据库中检索一些值。

下面的SQL与SQL Server数据源完美地兼容：

<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

但是当我更改查询以指向访问数据库中完全相同的表时，会收到错误消息：

<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

错误是这样的：

[Macromedia] [SequeLink JDBC驱动程序] [ODBC套接字] [Microsoft] [ODBC Microsoft Access驱动程序]语法错误（缺少运算符）在查询表达式“ COUNT（在DrawingTypeFK ='Civil'时为1，否则为null结束）。

有什么想法吗？ 我唯一的理论是它的访问驱动程序，但我使用此数据源的其他查询（无Count Case）都很好。

干杯尼尔

Answer 1

Access的数据库引擎不支持CASE ... WHEN ，因此您需要重写查询。 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()仅计算非Null值，因此应该给您我认为想要的东西。 但是，如果要使用Sum() ，如注释中所建议，这也应该起作用：

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

Answer 2

我尚未测试此代码，并且我想它的效率将比您的代码低得多，但它应可在MS Access中使用。 如果您的代码可以在所需的任何地方工作，那么我认为它比下面的代码更好。

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

这是一个相关的子查询，因此它可能非常慢。 买家当心。