Select Rows from Table1 NOT IN Table2 (t1.a = t2.a and t1.b = t2.b)

--Source(Table1 & Table2)

--Expected OutPut

DECLARE @T1 TABLE(A INT, B INT,C VARCHAR(10))
DECLARE @T2 TABLE(A INT, B INT,C VARCHAR(10))
INSERT INTO @T1(A,B,C)
VALUES (1,1,'SS1')
,(1,2,'SS2')
,(1,3,'SS3')


INSERT INTO @T2(A,B,C)
VALUES (1,1,'SS1')
,(1,2,'SS2')


--Method1:
SELECT A,B
FROM @T1
EXCEPT
SELECT A,B
FROM @T2
--Method2:
SELECT A.A,A.B
FROM @T1 A
left JOIN @T2 B ON A.A = B.A
AND a.B = b.B
WHERE b.B is null
--Method3:
SELECT * FROM @T1 AS T1
WHERE NOT EXISTS (SELECT 0
FROM @T2 AS T2
WHERE T2.A = T1.A
AND T2.B = T1.B
)
 
/*
 
I hope these will give the expected Result, Now i am looking over this which is best?
 
*/

String Concatenation Using XML Path

/*
Description : String concatenation using XML Path
This will help you to concatenate the reference table column values by using cross apply
*/
DECLARE @Table1 TABLE(CountryID INT,CountryName VARCHAR(50))
DECLARE @Table2 TABLE(StateID INT IDENTITY(1,1)
                                 ,CountryID INT
                                 ,StateName VARCHAR(50))

INSERT INTO @Table1(CountryID,CountryName) VALUES
(1 , 'USA'),
(2 , 'INDIA'),
(3 , 'AUSTRALIA')


INSERT INTO @Table2(CountryID,StateName) VALUES
(1,'Texas'),
(1,'Washington'),
(1,'New Yark'),
(1,'Colorodo'),
(2,'TamilNadu'),
(2,'Mumbai'),
(2,'Delhi'),
(2,'Banglore'),
(3,'Victoria'),
(3,'Tasmania'),
(3,'Queensland'),
(3,'New South Wales'),
(3,'Western Australia')


SELECT Table1.CountryID
,Table1.CountryName
,LEFT(StateNames,LEN(StateNames)- 1) AS StateNames
FROM @Table1 as Table1
CROSS APPLY
( SELECT StateName + ', '
FROM @Table2 AS Table2
WHERE Table2.CountryID = Table1.CountryID
FOR XML PATH('') ) AS State(StateNames)

--Desired Result

--* This Insert Statement will work in 2008 *