Convert SQL Code to SAS

[VALLY]

Convert SQL Code to SAS

please assist in converting the below code into SAS .

SELECT A.[KEY]

      ,A.[VOLUME]

      ,A.[DATE]

      ,A.[FLAG]

         --,[PREV_MONTH] = DATEADD(MONTH,-1,A.[DATE])

         ,[DIFFERENCE] = CASE

                                         WHEN CAST(A.[VOLUME] AS FLOAT) - CAST(B.[VOLUME] AS FLOAT) IS NULL THEN 0

                                         ELSE CAST(A.[VOLUME] AS FLOAT) - CAST(B.[VOLUME] AS FLOAT)

                                         END

         ,[SUM_] = CAST(A.[VOLUME] AS FLOAT) + CAST(B.[VOLUME] AS FLOAT)

  FROM [ATM Index].[dbo].[CIB_FINALE_2]                A

  LEFT JOIN [ATM Index].[dbo].[CIB_FINALE_2]    B

  ON          B.[KEY]  = A.[KEY]

              AND B.[FLAG] = A.[FLAG]

              AND MONTH(B.[DATE]) = MONTH(DATEADD(MONTH,-1,A.[DATE]))

  ORDER BY 1,3,4    

[Kurt_Bremser]

Rough try:

proc sql;
select
  a.key,
  a.date,
  a.flag,
  intnx('month',a.date,-1) as prev_month,
  case
    when (a.volume - b.volume) is missing then 0
    else (a.volume - b.volume)
  end as difference,
  sum(a.volume,b.volume) as sum_
from cib_finale a left join cib_finale b
on
  a.key = b.key and
  a.flag = b.flag and
  month(intnx('month',a.date,-1)) = month(b.date)
order by 1,3,4
;
quit;

Mind that this will cause problems if data from more than one year is present in the source table. Could it be that the MONTH function in the database returns a combination of year and month?