WHILE FUNCTION

CREATE FUNCTION [dbo].[inc] (@forLimit int)
RETURNS @Ints TABLE
(
  value int PRIMARY KEY
)
AS
BEGIN
DECLARE @index int
    SET @index = 0

    WHILE @index <= @forLimit BEGIN
          INSERT INTO @Ints VALUES (@index)
          SET @index = @index + 1
    END
    RETURN
END;

 SELECT * FROM group_set g
 Cross apply inc( 1) u