SELECT id FROM tableA
EXCEPT 
SELECT ClientId FROM tableB

SELECT id 
FROM tableA a
	LEFT JOIN tableB b  ON b.ClientID = a.id
WHERE b.id is null

(A UNION B) EXCEPT (A INTERSECT B)

A AND (NOT B)

SET NOCOUNT ON
--=======================================================================================
-- Recursive method shown by (Name with-held)
--=======================================================================================
  PRINT '========== Recursive method =========='
--===== Turn on some performance counters ===============================================
    SET STATISTICS IO ON
    SET STATISTICS TIME ON
DECLARE @BitBucket DATETIME --Holds display output so display times aren't measured.

--===== Execute the code being tested ===================================================
DECLARE @DateVal DATETIME
    SET @DateVal = '2008-01-01'

;with mycte as
     (
       select @DateVal AS DateVal
       union all
       select DateVal + 1
         from    mycte    
         where   DateVal + 1 < DATEADD(yy, 5, @DateVal)
     )
select @BitBucket = d.dateval
from mycte d
OPTION (MAXRECURSION 0)

--===== Turn off the performance counters and print a separator =========================
    SET STATISTICS TIME OFF
    SET STATISTICS IO OFF
  PRINT REPLICATE('=',90)
GO

--=======================================================================================
-- Tally table method by Jeff Moden
--=======================================================================================
  PRINT '========== Tally table method =========='
--===== Turn on some performance counters ===============================================
    SET STATISTICS IO ON
    SET STATISTICS TIME ON
DECLARE @BitBucket DATETIME --Holds display output so display times aren't measured.

--===== Execute the code being tested ===================================================
DECLARE @StartDate AS DATETIME
    SET @StartDate = '2008-01-01'

SELECT TOP (DATEDIFF(dd,@StartDate,DATEADD(yy,5,@StartDate)))
        @BitBucket = @StartDate-1+t.N 
   FROM Tally t
  ORDER BY N

--===== Turn off the performance counters and print a separator =========================
    SET STATISTICS TIME OFF
    SET STATISTICS IO OFF
  PRINT REPLICATE('=',90)