MS SQL 2014：将过程重写为CTE

Question

In MS SQL 2014 I've got a procedure that calculates years months and days in a way that from 5 years 14 months and 35 days I get 6 years 3 months and 5 days . Because I can use neither procedure (even temp) nor function in my code, I need that calculation into eg CTE. Can anyone help?

CREATE PROCEDURE #YearsMonthsDaysSum @EmpId INT
AS
BEGIN
DECLARE @Years INT, @Months INT, @Days INT
SELECT @Years=Years, @Months=Months, @Days=Days FROM #Table1 WHERE EmpId=@EmpId
IF @Days<0
BEGIN
    SET @Months=@Months-(1-CAST(@Days/30 as INT))
    SET @Days=@Days+30*(1-CAST(@Days/30 as INT))
END
IF @Months<0
BEGIN
    SET @Years=@Years-(1-CAST(@Months/12 as INT))
    SET @Months=@Months+12*(1-CAST(@Months/12 as INT))
END
IF(@Days>30)
BEGIN
    SET @Months=@Months+CAST(@Days/30 as INT)
    SET @Days=@Days%30
END
IF(@Months>=12)
BEGIN
    SET @Years=@Years+CAST(@Months/12 as INT)
    SET @Months=@Months%12
END

SELECT EmpId=@EmpId, Years=@Years, Months=@Months, Days=@Days
END

Answer 1

It would be easier to first calculate the total number of days, then get back to years,months and days.

declare @empid int = 1
Declare @table1 table (empid int, years int, months int, [days] int)
insert into @table1 values (1,5,14,35)

;with YearsMonthsDaysSum_cte as
(
    select days/(30*12) years,(days%(30*12))/30 months,days%30 [days]
    from (
        select  [days] + months * 30 + years * 30*12 [days]
        from @table1) x
    )

select * from YearsMonthsDaysSum_cte

Answer 2

Using CROSS APPLY for in-line calculations eliminates CTE. Just

SELECT EmpId, step2.Years, step2.Months, step2.Days
    FROM #Table1 t
    CROSS APPLY (
      SELECT totaldays = [days] + months * 30 + years * 30*12 [days]
    ) step1 
    CROSS APPLY (
      SELECT 
        years = totaldays/(30*12), 
        months = totaldays%(30*12))/30,
        [days] = totaldays%30 
    ) step2
  -- JOIN, WHERE or any other Sql follows
;

More steps can be added for complex calculations, leap years for example.