items in list A that dont appear in list B (was "Simple Query...I think")

Ok, I want to write a stored procedure / query that says the following:
Code:
If any of the items in list 'A' also appear in list 'B' --return false
If none of the items in list 'A' appear in list 'B' --return true

In pseudo-SQL, I want to write a clause like this

Code:

IF
(SELECT values FROM tableA) IN(SELECT values FROM tableB)
Return False
ELSE
Return True


Unfortunately, it seems I can't do that unless my subquery before the 'IN' statement returns only one value. Needless to say, it returns a number of values.

I may have to achieve this with some kind of logical loop but I don't know how to do that.

Can anyone help?OK so it wasnt' so simple...at least MY solution isn't:

SET QUOTED_IDENTIFIER ON
GO
SET ANSI_NULLS ON
GO

ALTER PROC sp_get_trolley_inconsistencies
@.grower CHAR(2),
@.load_id INT
AS

DECLARE @.ID int,
@.TrolleyList varchar(300),
@.Date DATETIME
--Get the relevant date from the DB Table
SELECT @.Date = (SELECT CONVERT(DATETIME, rl_eta, 102) FROM requi_load WHERE rl_id = @.load_id)

SET @.TrolleyList = ''
--Get the list of values into a comma delimited string
DECLARE crs_Trolleys CURSOR
FOR SELECT DISTINCT ldl_trolley
FROM load_detail_lines
WHERE ldl_requi_load_id = @.load_id

OPEN crs_Trolleys
FETCH NEXT FROM crs_Trolleys INTO @.ID

WHILE @.@.FETCH_STATUS = 0
BEGIN
SELECT @.TrolleyList = @.TrolleyList+CAST(@.ID AS varchar(5))+ ', '
FETCH NEXT FROM crs_Trolleys INTO @.ID
END

SET @.TrolleyList = SUBSTRING(@.TrolleyList,1,DATALENGTH(@.TrolleyList)-2)

CLOSE crs_Trolleys
DEALLOCATE crs_Trolleys

--Parse the string and run the 'IN' statement on each of the Parsed Values

DECLARE @.parsingList VARCHAR(300)
DECLARE @.find_comma INT
DECLARE @.trolleytocheck VARCHAR(4)

SELECT @.parsingList = @.TrolleyList

WHILE @.parsingList IS NOT NULL

BEGIN
SELECT @.find_comma = PATINDEX('%,%',@.parsingList)
IF @.find_comma <> 0
BEGIN
SELECT @.trolleytocheck = SUBSTRING(@.parsingList,1,(@.find_comma-1))
SELECT @.parsingList = LTRIM(SUBSTRING(@.parsingList,(@.find_comma+1),300))
PRINT @.trolleytocheck
IF @.trolleytocheck IN(SELECT distinct ldl_trolley
FROM load_detail_lines, requi_load
WHERE ldl_requi_load_id = rl_id
AND ldl_requi_load_id NOT LIKE @.load_id
AND rl_status = 1
AND DAY(rl_eta) = DAY(@.Date)
AND MONTH(rl_eta) = MONTH(@.Date)
AND YEAR(rl_eta) = YEAR(@.Date))
BEGIN
RAISERROR 50001 'Error! You screwed up, trolley '
END
CONTINUE
END
ELSE
BEGIN
--this block finds the last value in the trolley list
SELECT @.trolleytocheck = @.parsingList
SELECT @.parsingList = null
PRINT @.trolleytocheck
BREAK
END
END

GO
SET QUOTED_IDENTIFIER OFF
GO
SET ANSI_NULLS ON
GO

If anyone can suggest anything more elegant...please let me know.|||Why not join the tables and count the rows that match?|||Doh!

*Commits ritual suicide*