在IIF语句中使用存在子句

Question

我们可以在IIF语句中使用Exists子句吗？我想根据特定条件订购输出。

Select *
From Table1 AS a
Order By IIF( Exists(Select * From Table2 Where Col_Name='Criteria'),a.Col1,a.Col2) Desc

无法在MS Access中获得结果。

Answer 1

将DLookUp或DCount域功能视为EXISTS子句，在MS Access表达式中不起作用：

Select *
From Table1 AS a
Order By IIF(DLookUp("Col_Name", "Table2", "Col_Name='Criteria'") IS NOT NULL, a.Col1, a.Col2) Desc

Select *
From Table1 AS a
Order By IIF(DCount("*", "Table2", "Col_Name='Criteria'") > 0, a.Col1, a.Col2) Desc