Question

Not sure how to word this. Say i have a select returing this.

Name, month, amount
John, June, 5
John, July,6
John, July, 3
John August, 10

and I want to aggregate and report beggining blance for each month.

name, month, beggining balance.

john, may, 0
john, june, 0
john, july, 5
john, august, 14
john, September, 24

I can do this in excel with cell formulas, but how can I do it in SQL without storing values somewhere? I have another table with fiscal months i can do a left outer join with so all months are reported, just not sure how to aggregate from prior months in sql.

Answer 1

select
name
, month
, (select sum(balance) from mytable 
   where mytable.month < m.month and mytable.name = m.name) as starting_balance
from mytable m
group by name, month

This is not as nice as windowing functions, but since they vary from database to database, you’d need to tell us which system you are using.

And it’s an inline subquery, which is not very performant. But at least it’s easy to understand what’s going on !