Following User Defined Function (UDF) returns the numbers of days in month. It is very simple yet very powerful and full proof UDF.
CREATE FUNCTION [dbo].[udf_GetNumDaysInMonth] ( @myDateTime DATETIME )
RETURNS INT
AS
BEGIN
DECLARE @rtDate INT
SET @rtDate = CASE WHEN MONTH(@myDateTime)
IN (1, 3, 5, 7, 8, 10, 12) THEN 31
WHEN MONTH(@myDateTime) IN (4, 6, 9, 11) THEN 30
ELSE CASE WHEN (YEAR(@myDateTime) % 4 = 0
AND
YEAR(@myDateTime) % 100 != 0)
OR
(YEAR(@myDateTime) % 400 = 0)
THEN 29
ELSE 28 END
END
RETURN @rtDate
END
GO
Run following script in Query Editor:
SELECT dbo.udf_GetNumDaysInMonth(GETDATE()) NumDaysInMonth
GO
ResultSet:
NumDaysInMonth
———————–
31
Reference : Pinal Dave (https://blog.sqlauthority.com)
