PostgreSQL Select every fifteen day of month - sql

Question

Hello i have some record:
date Money
1/6/2014 100
12/6/2014 2200
13/6/2014 500
1/3/2014 100
2/5/2014 2200
30/5/2014 500
30/6/2014 100
23/6/2014 2200
31/6/2014 500
Well, i have one param, its date for example i need all record of 30 of july but i need the sum of record if very easy that
select sum(money) from info where date <= param
group by month
But now i need all record group by day of month but i need every fifteen for every month to lower the parameter in my result i need for example
param = 30/6/2014
The result I hope to get:
15/6/2014 sum(money)
15/5/2014 sum(money)
15/4/2014 sum(money)
I need the record for every fifteen of month

Answer 1

The question is how to arrange it to days up to the 15th are in one month and days from the 16th onward are in the next month. You can do this by subtracting 15 days. This puts all days from 1-15 in the previous month. Then, add a month. Here is an approach in Postgres:
select to_char(date - 15 * interval '1 day' + interval '1 month', 'YYYY-MM') as mon,
sum(money)
from info
where date <= param
group by to_char(date - 15 * interval '1 day' + interval '1 month', 'YYYY-MM')
order by 1;
EDIT:
If you want month-to-the-15th, then you can do:
select to_char(date, 'YYYY-MM') as mon,
sum(money)
from info
where extract(day from date) <= param
group by to_char(date, 'YYYY-MM')
order by 1;
Or, if it is only for one month:
select sum(money)
from info
where to_char(date, 'YYYY-MM') = to_char(param, 'YYYY-MM') and
date <= param;