Re: Combining two SELECTs by same filters

On Wed, 2005-10-26 at 10:16, Volkan YAZICI wrote:

> => SELECT
> -> (SELECT count(id) FROM sales
> -> WHERE id = 2
> -> AND date_trunc('hour', dt) = '2005-10-25 21:00:00'),
> -> (SELECT count(id) FROM sales
> -> WHERE id = 2
> -> AND date_trunc('hour', dt) = '2005-10-25 22:00:00');
> ?column? | ?column?
> ----------+----------
> 6 | 2
> (1 row)
>
> Isn't it possible to combine these two SELECTs as one. Because one of
> their filters are same: id = 2. I'm just trying to avoid making 2
> scans with nearly same filters.

Do something like this:

select count(id)
from sales
where id=2 and
dt between 'firstdatehere' and 'lastdatehere'
group by date_trunc('hour', dt);