Your query looks suspiciously complicated...
Why not process all 12 months in one shot with something like this :
- only one subquery
- no join
- date between can make an index scan on date
select category, sum(amount) as sum_amount, extract (month from date) as
month
from all_accounts where (date between beginning of the year and end of
the year)
group by category,month order by category,month )
Not what you wanted but probably massively faster.
Or you can do this (in approximate SQL):
create type annual_report_type as
( sums numeric(9,2)[12] );
create type my_type as ( month integer, amount numeric );
CREATE AGGREGATE my_sum
takes one input which is my_type and sums the amount into the month column
of annual_report_type
Then :
select category, my_sum( my_type(month,amount) as report, extract (month
from date) as month
from all_accounts where (date between beginning of the year and end of
the year)
group by category,month order by category,month )
Dunno if this would work, it would be nice I think.