How to get week start and end date string in PostgreSQL?

Question

I am using PostgreSQL 8.3. I have a table like this:

id        regist_time        result
-----------------------------------
1     2012-07-0         


        

Answer 1

select date_trunc('week', regist_time)::date || ' - ' ||
       (date_trunc('week', regist_time) + '6 days') ::date as Week,
       sum(result) Total
from YourTable
group by date_trunc('week', regist_time)
order by date_trunc('week', regist_time)

See proof of concept at SQLFiddle: http://sqlfiddle.com/#!1/9e821/1