如何在 SQL Server 中获取上一季度的月份和年份

Question

• If the date is 2020-07-14, output month:3 year:2020
  previous-previous quarter is 1 and 1st quarter last month is 3

• If the date is 2020-03-14, output month:9 year:2019
  previous-previous quarter is 3 and 3rd quarter last month is 9

Did this for Month:

declare @month int;
declare @quarter int

set @quarter= DATEPART(Quarter, '2020-10-14')
set @month = (@quarter - 2) *3

select @month
select @quarter

Please do help me with the year. I have searched online gone through Datediff and dateadd functions but it is confusing

Answer 1

If it is the last day of the quarter then here is one solution. This should work going forwards and backwards.

DECLARE @ReportDate DATETIME = '2020-07-14'
DECLARE @QuarterInterval INT = -2

DECLARE @EndOfQuarter DATETIME =(SELECT DATEADD(DAY, -1, DATEADD(QUARTER, DATEDIFF(QUARTER, 0,DATEADD(QUARTER,@QuarterInterval , @ReportDate)) +1, 0)))

SELECT 
    TheDate = @EndOfQuarter,
    TheMonth = DATEPART(MONTH,@EndOfQuarter),
    TheYear = DATEPART(YEAR,@EndOfQuarter)

Answer 2

I think I'd find it easier to adjust the date to the first day of the final month of the current quarter then take 6 months off it:

declare @quart int;
declare @month int;
declare @thedate date;
set @thedate = '2020-07-14';
set @quart = DATEPART(quarter, @thedate);
set @month = ((@quart - 1) * 3) + 2
set @thedate = DATEFROMPARTS(@year, @month, 1)
set @thedate = DATEADD(month, @thedate, -6)

If it's the last day of the quarter before last quarter you can use the EOMONTH function to turn this date into the last day of the month rather than the first

You could also consider taking your current date, adding (((MONTH(date) - 1) % 3) - 6) months to it then EOMONTHing it. The formula produces either -4, -5 or -6 depending on whether the month is the first second or third in the quarter (7th is the first month of q3, it becomes -4, and 7-4 = 3, March, the last month of q1). EOMONTH will put the date to last in the month at the end of the math

Answer 3

You can give this a try:

declare @month int;declare @edate date,@year int;
set @edate= dateadd(qq, DateDiff(qq, 0, Dateadd(Month,-6,'2020-07-14'))+1,-1)
set @month=month(@edate)
set @year=year(@edate)
select @month
select @year