My Initial Data Sample Still valid ...but I mentioned the all possible Combinations in my latest post

DECLARE @ClassID TABLE (Class INT, Product INT)

DECLARE @ProductClass TABLE(Product INT, Class INT)

---@ProductClass table Product is pk

INSERT INTO @ClassID

SELECT 1000, 100

UNION ALL SELECT 2000, 100

UNION ALL SELECT 3000, 100

UNION ALL SELECT 1000, 100

UNION ALL SELECT 2000, 100

INSERT INTO @ProductClass

SELECT 200, 1000

UNION ALL SELECT 300, 1000

UNION ALL SELECT 400, 1000

UNION ALL SELECT 500, 2000

UNION ALL SELECT 600, 2000

UNION ALL SELECT 800, 3000

UNION ALL SELECT 900, 3000

Result Set as below

Group ID||Item Group ID ( Auto Generated)||Product ID

11200

11500

11800

12200

12600

12800

13200

13500

13900

14200

14600

14900

15300

15500

15800

16300

16600

16800

17300

17500

17900

18300

18600

18900

19400

19500

19800

110400

110600

110800

111400

111500

111900

112400

112600

112900

21200

21500

22200

22600

23300

23500

24300

24600

25400

25500

26400

26600