Re: counts of groupings by date year-month

On Fri, Feb 27, 2009 at 2:02 PM, Carol Cheung
<cacheung(at)consumercontact(dot)com> wrote:
> Hi,
> I have a table called temp
>
>  access_date | active | status
> -------------+--------+--------
>  2009-02-01  | t      |     15
>  2009-02-01  | f      |     16
>  2009-02-02  | f      |     17
>  2009-02-01  | t      |     17
>  2009-02-02  | f      |     21
>  2009-01-01  | t      |     20
>  2009-01-01  | t      |     21
>  2009-01-01  | f      |     21
>
>
> What I want is to be able to get counts of active by year-month. So the
> output would be like:
>
>  year_month | count
> ------------+-------
> 200901      | 3
> 200902      | 5
>
> I tried something like
> SELECT to_char(access_date, 'YYYYMM') as year_month, count(year_month) FROM
> temp GROUP BY year_month ORDER BY year_month;
>
> but I'm unable to execute this query because the column "year_month" doesn't
> exist in temp table.

Try date_trunc:

select date_trunc('day',timestamp), count(*) from table where active
is true group by date_trunc('day',timestamp) order by
date_trunc('day',timestamp);