Using CASE Statement inside IN Clause

Question

Is is possible to use a CASE statement inside an IN clause?

This is a simplified version of what I have been trying to get to compile correctly:

SELECT * FROM MyTable 
WHERE StatusID IN (
CASE WHEN @StatusID = 99 THEN (5, 11, 13)
ELSE (@StatusID) END )

Thanks!

Answer 1

CASE returns a scalar value only. You can do this instead. (I am assuming, as per your example, that when @StatusID = 99, a StatusID value of 99 is not a match.)

select *
from MyTable
where (@StatusID = 99 and StatusID in (5, 11, 13))
    or (@StatusID <> 99 and StatusID = @StatusID)

Answer 2

No. Instead, you can put it outside

SELECT *
FROM MyTable
WHERE 1 = (CASE WHEN @StatusID = 99 and StatusId in (5, 11, 13) then 1
                WHEN coalesce(@StatusId, 0) <> 99 and StatusId in (@StatusID) then 1
                ELSE 0
           END)

You can also write this without the case statement.

Another option is dynamic SQL, where you actually create a string with the SQL statement and then execute it. However, dynamic SQL seems like overkill in this case.

Answer 3

I thought I'd attempt this differently using a Table Valuue Constructor - are TVCs not allowed in the following context?

SELECT * 
FROM MyTable  
WHERE StatusID IN 
   ( 
   SELECT 
       CASE 
         WHEN @StatusID = 99 THEN (values(5),(11),(13)) t(StatusID )
         ELSE @StatusID 
   END  
   ) 

Answer 4

You can do this using TVCs, but the approach is a little different. It doesn't use case, but it will scale more nicely where there are a number of possible options to choose from:

SELECT * 
FROM MyTable  
join (values 
      (99,5),(99,11),(99,13),
      (@StatusID , @StatusID)    
    ) t(k,v) on t.k= @StatusID and t.v = StatusID)

or if you need everything in the where clause then:

SELECT * 
FROM MyTable  
WHERE exists (
    select 1
    from (values 
      (99,5),(99,11),(99,13),
      (@StatusID , @StatusID)    
    ) t(k,v)
    where t.k= @StatusID and t.v = StatusID)