SET @Count = (SELECT COUNT(*) FROM UserTable WHERE Username = @Username AND Password = @Password)
IF @Count > 0
BEGIN
    SET @SessionID = CONVERT(varchar(32), NEWID())
    PRINT 'IF Clause'
    SET @Response = @SessionID
END
ELSE
BEGIN
    PRINT 'ELSE Clause'
    SET @Response = 'error 401'
END

IF (SELECT COUNT(*) FROM UserTable WHERE Username = @Username AND Password = @Password) > 1

IF EXISTS (SELECT * FROM UserTable WHERE Username = @Username AND Password = @Password)