CREATING CALCULATION ON THE SAME FIELD

Question

I want to create a calculation where I can get the movement in balance from one period to the next (the periods are specified in parameters), eg End balance sum of Dec 07 less End balance sum of Mar 08.
There is a similar query where I want to compare the balances held in different sets of books. eg End balance sum of sob id 93 less End balance sum of sob id 94.
Would appreciate any pointers. Thanks

Answer 1

create table t(d date, n number, t varchar2(40));
alter session set nls_date_format='DD.MM.RR';
insert into t values (to_date('01/01/05'),1000,'credit');
insert into t values (to_date('02/01/05'),500,'credit');
insert into t values (to_date('02/01/05'),200,'debit');
insert into t values (to_date('01/01/05'),2000,'debit');
insert into t values (to_date('01/01/05'),3000,'debit');
insert into t values (to_date('01/01/05'),12,'credit');
insert into t values (to_date('02/01/05'),12,'credit');
select d,
    sum(n*instr(t,'debit')) debit,
    sum(n*instr(t,'credit')) credit
from t
group by d;
D             DEBIT     CREDIT
01.01.05       5000       1012
02.01.05        200        512