How can I get a real difference between two dates in months?-CodePudding

My problem is, when I set the date range as the following

DECLARE @startdate DATETIME2 = '2023-01-31 08:00:00.0000000';  
DECLARE @enddate   DATETIME2 = '2023-02-01 08:00:00.0000000';   
SELECT DATEDIFF(month, @startdate, @enddate)

The result is one.

CodePudding user response：

Perhaps more that you are looking for, but here is a Table-Valued Function. Can be called individually or within a CROSS APPLY if your data is in a table.

Example

DECLARE @startdate DATETIME2 = '2023-01-31 08:00:00.0000000';  
DECLARE @enddate   DATETIME2 = dateadd(month,6,getdate()) --'2023-02-01 08:00:00.0000000';   

Select * 
From [dbo].[tvf-Date-Elapsed](@startdate,@enddate)

Results

Years   Months  Days    Hours   Minutes Seconds
0       5       24      3       2       49

The function if interested

CREATE FUNCTION [dbo].[tvf-Date-Elapsed] (@D1 DateTime,@D2 DateTime)
Returns Table
Return (
    with cteBN(N)   as (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
         cteRN(R)   as (Select Row_Number() Over (Order By (Select NULL))-1 From cteBN a,cteBN b,cteBN c),
         cteYY(N,D) as (Select Max(R),Max(DateAdd(YY,R,@D1))From cteRN R Where DateAdd(YY,R,@D1)<=@D2),
         cteMM(N,D) as (Select Max(R),Max(DateAdd(MM,R,D))  From (Select Top 12 R From cteRN Order By 1) R, cteYY P Where DateAdd(MM,R,D)<=@D2),
         cteDD(N,D) as (Select Max(R),Max(DateAdd(DD,R,D))  From (Select Top 31 R From cteRN Order By 1) R, cteMM P Where DateAdd(DD,R,D)<=@D2),
         cteHH(N,D) as (Select Max(R),Max(DateAdd(HH,R,D))  From (Select Top 24 R From cteRN Order By 1) R, cteDD P Where DateAdd(HH,R,D)<=@D2),
         cteMI(N,D) as (Select Max(R),Max(DateAdd(MI,R,D))  From (Select Top 60 R From cteRN Order By 1) R, cteHH P Where DateAdd(MI,R,D)<=@D2),
         cteSS(N,D) as (Select Max(R),Max(DateAdd(SS,R,D))  From (Select Top 60 R From cteRN Order By 1) R, cteMI P Where DateAdd(SS,R,D)<=@D2)

    Select [Years]   = cteYY.N
          ,[Months]  = cteMM.N
          ,[Days]    = cteDD.N
          ,[Hours]   = cteHH.N
          ,[Minutes] = cteMI.N
          ,[Seconds] = cteSS.N
          --,[Elapsed] = Format(cteYY.N,'0000') ':' Format(cteMM.N,'00') ':' Format(cteDD.N,'00') ' ' Format(cteHH.N,'00') ':' Format(cteMI.N,'00') ':' Format(cteSS.N,'00')
     From  cteYY,cteMM,cteDD,cteHH,cteMI,cteSS
)
--Max 1000 years
--Select * from [dbo].[tvf-Date-Elapsed] ('1991-09-12 21:00:00.000',GetDate())