Question

Possible Duplicate:
MySQL query that computes partial sums

ok, the question is not clear at all so the example would be:
i have a table like this:

id     amount

1       1000
2       2500
3       5000

and i need to select from it the following data:

id     oamount     total

1       1000      1000
2       2500      3500
3       5000      8500

i tried this but it is not correct:

    select *,sum(oamount) from `table` 
group by id;

and i can’t figure it out

Answer 1

I’ve answered a very similar where they were trying to get cash flow balances for beginning / ending of each day… Found here

Yours would be very similar… Prequery the data in the final order you want it (ie: starting ID would be the first of the result set), then apply what you want with MySQL Variables

select
      PreAgg.ID,
      PreAgg.Amount,
      @PrevBal := @PrevBal + PreAgg.Amount as Total
   from 
      ( select
              YT.id,
              YT.amount
           from
              YourTable YT
           order by
              YT.id ) as PreAgg,
      ( select @PrevBal := 0.00 ) as SqlVars

I’ve actually kept the pre-aggregate as a query… in case you wanted to actually DO some aggregations like based on transactions on a daily basis, or applied some other WHERE clause. This would allow flexibility to ensure your final output order was prepared BEFORE starting your @PrevBal accumulation.