Re: How to join several selects

On 8/24/05 9:46 AM, "Josep Sanmartí" <josep(dot)sanmarti(at)openwired(dot)net> wrote:

> Hello,
> I have a 'big' problem:
> I have the following table users(name, start_time, end_time), a new row
> is set whenever a user logs into a server. I want to know how many
> users have logged in EVERYDAY between 2 different dates. The only idea
> that I have is making several select (one for each day):
> SELECT COUNT(name) FROM users WHERE start_time between "startDate"
> and "startDate+1"
> SELECT COUNT(name) FROM users WHERE start_time between "startDate+1"
> and "startDate+2"
> ...
> I would like to know if its possible to make it in 1 sql statement or
> just which is the best efficient way to solve it.
> By the way, I use Postgres 7.4.

See:

http://www.postgresql.org/docs/8.0/interactive/sql-select.html#SQL-UNION
like:

SELECT COUNT(name) FROM users WHERE start_time between "startDate"
and "startDate+1"
union
SELECT COUNT(name) FROM users WHERE start_time between "startDate+1"
and "startDate+2"

Sean