Question

I want to accomplish the following from case when

If @chk='Y'  
    Select * From Table1 Where Column1=@Value  
Else If (@chk='N')
    Select * From Table1 Where Column1 In (Select column2 from Table2)

I think it may be something like:

 Select * 
 From Table1 
 Where 
    Case  When @chk='Y' Then
        Column1=@Value
    Else
        Column1 In (Select column2 from Table2)
 End

I know there are alternative solutions other than Case When. But is it possible to do this using Case when?

Answer 1

CASE is an expression that returns a single value. It is not used for control of flow.

WHERE (Column1 = @Value AND @chk = 'Y')
OR (@chk <> 'Y' AND Column1 IN (SELECT column2 FROM table2));