Now you can add additional Hierarchies, without changing the code ...

INSERT INTO tblMonths ( MonthKey, Name, ParentKey )

Values (19, 'OddMonths', 1)

, (20, 'EvenMonths', 1)

, ( 6, 'Jan', 19)

, ( 7, 'Feb', 20)

, ( 8, 'Mar', 19)

, ( 9, 'Apr', 20)

, (10, 'May', 19)

, (11, 'Jun', 20)

, (12, 'Jul', 19)

, (13, 'Aug', 20)

, (15, 'Sep', 19)

, (16, 'Oct', 20)

, (17, 'Nov', 19)

, (18, 'Dec', 20);