gistfile1.txt

DECLARE 
    @a bit = 0,
    @b bit = 0,
    @r varchar(5) = '';

/*This was 100x faster*/
IF @b = 0 AND @a = 0 
  RETURN 'S';
IF @b = 0 AND @a = 1 
  RETURN 'A';
IF @b = 1 AND @a = 0 
  RETURN 'B';
RETURN 'AB';

/*Than doing this*/
IF @b = 0 AND @a = 0 
  SET @r = 'S';
IF @b = 0 AND @a = 1 
  SET @r = 'A';
IF @b = 1 AND @a = 0 
  SET @r = 'B';
ELSE 
  SET @r = 'AB'
RETURN @r;