how to calculate balances in an accounting software using postgres window function

Question

I\'ved got a problem same as this but I am using Postgres.

Calculate balance with mysql

have a table which contains the following data:

ID            


        

Answer 1

select t.*, sum("In"-"Out") over(order by id) as balance
from tbl t
order by id

Fiddle: http://sqlfiddle.com/#!15/97dc5/2/0

Consider changing your column names "In" / "Out" so that you don't need to put them in quotes. (They are reserved words)

If you wanted only one customer (customer_id = 2):

select t.*, sum("In"-"Out") over(order by id) as balance
from tbl t
where customer_id = 2
order by id

If your query were to span multiple customers and you wanted a running balance that RESTARTED with each customer, you could use:

select t.*, sum("In"-"Out") over( partition by customer_id
                                  order by customer_id, id ) as balance_by_cust
from tbl t
order by customer_id, id