Greatest/Least ivf

CREATE FUNCTION [dbo].[ivf_least] (@1 datetime=null,@2 datetime = null ,@3 datetime = null,@4 datetime=null,@5 datetime = null)
RETURNS TABLE WITH SCHEMABINDING
RETURN
(WITH coal(a1,a2,a3,a4,a5)
AS (SELECT COALESCE(@1,@2,@3,@4,@5),COALESCE(@2,@3,@4,@5,@1),COALESCE(@3,@4,@5,@1,@2),COALESCE(@4,@5,@1,@2,@3),COALESCE(@5,@1,@2,@3,@4))
SELECT case when a1<=a2 and a1<=a3 and a1<=a4 and a1<=a5 then a1
when a2<=a3 and a2<=a4 and a2<=a5 then a2
when a3<=a4 and a3<=a5 then a3
when a4<a5 then a4
else a5 end as out from coal);
GO

ALTER FUNCTION [dbo].[ivf_greatest] (@1 datetime=null,@2 datetime = null ,@3 datetime = null,@4 datetime=null,@5 datetime = null)
RETURNS TABLE WITH SCHEMABINDING
RETURN
(WITH coal(a1,a2,a3,a4,a5)
AS (SELECT COALESCE(@1,@2,@3,@4,@5),COALESCE(@2,@3,@4,@5,@1),COALESCE(@3,@4,@5,@1,@2),COALESCE(@4,@5,@1,@2,@3),COALESCE(@5,@1,@2,@3,@4))
SELECT case when a1>=a2 and a1>=a3 and a1>=a4 and a1>=a5 then a1
when a2>=a3 and a2>=a4 and a2>=a5 then a2
when a3>=a4 and a3>=a5 then a3
when a4>a5 then a4
else a5 end as out from coal);
GO