SQL-根据YTD编号计算得出的MTD编号

Question

we have a YTD report which is run on a monthly basis. I would like to calculate the MTD movement for each month by doing a calculation of Month+1 minus Month0 = MTD

Data as per below in one table

Month | Account | YTD amount
Jan   | AB123   | 100
Feb   | AB123   | 200
Mar   | AB123   | 350

I have many accounts which I would need a running MTD like below.

Month | Account | MTD Amount
Jan   | AB123   | 100
Feb   | AB123   | 100
Mar   | AB123   | 150

I read you can do a self join which could search for a different line within the same table. But I can't quite get how you could do this multiple times if you have 3+ months. Having Jan and Feb looks straight forward.

SELECT A.[Month]
  ,A.[Account]
  ,A.[YTD] FebYTD
  ,B.[YTD] JanYTD
  ,A.[YTD] - B.[YTD] MTD
FROM 
(
SELECT [Month]
   ,[Account]
   ,[YTD]
FROM [PWC_2017].[dbo].[MTD test]
where [Month] = 'Feb'
) A
join
(
SELECT [Month]
  ,[Account]
  ,[YTD]
FROM [PWC_2017].[dbo].[MTD test]
Where [Month] = 'Jan'
) B
on A.[Account] = B.[Account]

Results below

Month | Account | FebYTD | JanYTD | MTD
Feb   | AB123   |   200  |  100   | 100

I'd like to do one query which I could run each month. So for example, when September month comes around, it's going to give me 9 rows of MTD. Jan-Sep. Basically it will run on all the months available in the table at the current time. Thanks.

Answer 1

one minor addition to the above.

Based on premise of comparing to YTD- 1 and having included a case for the MTD, although the January is solved for the example it doesn't work eg when data is only recorded ao March. The first MTD will be NULL.

So I simply, added a zero when no previous YTD exists,

CASE CurrentYTD.Month_ID
WHEN 1 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0) 
WHEN 2 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 3 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 4 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 5 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 6 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 7 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 8 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 9 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 10 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 11 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
WHEN 12 Then COALESCE (CurrentYTD.Amount,PreviousYTD.Amount)- COALESCE(PreviousYTD.Amount,0)
END AS Amount_MTD

Answer 2

You could try the following query

SELECT Current.[Month], 
       Current.[Account], 
       Current.[YTD]                                       CurrentYTD, 
       Next.[YTD]                                          NextYTD, 
       COALESCE(Next.[YTD], Current.[YTD]) - Current.[YTD] MTD 
FROM   (SELECT [Month], 
               CASE [Month] 
                 WHEN 'Jan' THEN 1 
                 WHEN 'Feb' THEN 2 
                 WHEN 'Mar' THEN 3 
                 WHEN 'Apr' THEN 4 
                 WHEN 'May' THEN 5 
                 WHEN 'June' THEN 6 
                 WHEN 'July' THEN 7 
                 WHEN 'Aug' THEN 8 
                 WHEN 'Sept' THEN 9 
                 WHEN 'Oct' THEN 10 
                 WHEN 'Nov' THEN 11 
                 WHEN 'Dec' THEN 12 
               END AS [MonthId], 
               [Account], 
               [YTD] 
        FROM   [PWC_2017].[dbo].[MTD test]) Current 
       LEFT JOIN (SELECT [Month], 
                         CASE [Month] 
                           WHEN 'Jan' THEN 1 
                           WHEN 'Feb' THEN 2 
                           WHEN 'Mar' THEN 3 
                           WHEN 'Apr' THEN 4 
                           WHEN 'May' THEN 5 
                           WHEN 'June' THEN 6 
                           WHEN 'July' THEN 7 
                           WHEN 'Aug' THEN 8 
                           WHEN 'Sept' THEN 9 
                           WHEN 'Oct' THEN 10 
                           WHEN 'Nov' THEN 11 
                           WHEN 'Dec' THEN 12 
                         END AS [MonthId], 
                         [Account], 
                         [YTD] 
                  FROM   [PWC_2017].[dbo].[MTD test]) Next 
              ON Current.[Account] = Next.[Account] 
                 And Current.[MonthId] + 1 = Next.[MonthId]