Question

I need a temporary solution to a problem I’ve created. Essentially I want to calculate two values, but use a different method dependant on the result of a condition.

select userReturnval, userregisterid, OtherValue
FROM
(
   (SELECT otherValue
   FROM...
   ) as tblO  --unrelated table
  ,

  ( 
    if (select count(userregisterid) from table1 where site =@siteID and userid=@userID) >0
      SELECT userReturnval, userregisterid
    FROM
    (
     SELECT userReturnval, userregisterid, Rank() OVER (PARTITION BY .. ORDER BY       ...) as RANK
            FROM ...
            WHERE --first where clause
        ) as tblRank
        WHERE (RANK =1)
    else
      SELECT userReturnval, userregisterid
      FROM
        (
     SELECT userReturnval, userregisterid, Rank() OVER (PARTITION BY .. ORDER BY       ...) as RANK
            FROM ...
            WHERE --different where clause
        ) as tblRank
        WHERE (RANK =1)

  ) as tblR

My if works fine on its own, I just to get it working as part of the larger query. At the moment, sqlserver doesn’t like the if being in there.

Hopefully someone can point me in the right direction!

Answer 1

You can try using case statements in the WHERE clause, something like the statement below. Note that I don’t think this will be particularly optimal for performance.

Doing it like this does allow you to keep it to a single statement though:

select userReturnval, userregisterid, OtherValue
FROM
(
   (SELECT otherValue
   FROM...
   ) as tblO  --unrelated table
  ,

  ( 
    SELECT userReturnval, userregisterid
    FROM
    (
     SELECT userReturnval, userregisterid, Rank() OVER (PARTITION BY .. ORDER BY       ...) as RANK
            FROM ...
            WHERE 
                case --Choose which where clause to use
                    when (select count(userregisterid) from table1 where site =@siteID and userid=@userID) >0 then 
                        case when /*First where clause*/ then 1
                        else 0
                        end
                    else
                        case when /*Second where clause*/ then 1
                        else 0
                        end
                    end
                 = 1                
        ) as tblRank
        WHERE (RANK =1)
  ) as tblR