Re: Drawing a blank on some SQL

From: Rob Sargent <robjsargent(at)gmail(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: Drawing a blank on some SQL
Date: 2011-02-11 19:17:08
Message-ID: 4D558B34.50901@gmail.com
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On 02/11/2011 11:46 AM, Aaron Burnett wrote:
>
> Hi,
>
> I'm just drawing a blank entirely today and would appreciate some help on
> this.
>
> The long and short; there are 12 distinct activities that need to be queried
> on a weekly basis:
>
> SELECT count(activity_id), activity_id
> FROM foo_activity
> WHERE created >= '01/01/2011' and created < '01/08/2011'
> GROUP BY 2
> ORDER BY 2;
>
> It gives me this answer, which is correct:
>
> count | activity_id
> -------+---------------------
> 1502 | 1
> 11 | 2
> 2 | 3
> 815 | 4
> 4331 | 7
> 30 | 9
> 1950 | 10
> 7 | 11
> 67 | 12
>
> But what I need to see is if there are no activities for the particular
> activity_id that week, that it lists the count as 0 and lists the
> activity_id associated like this:
>
> count | activity_id
> -------+---------------------
> 1502 | 1
> 11 | 2
> 2 | 3
> 815 | 4
> 0 | 5
> 0 | 6
> 4331 | 7
> 0 | 8
> 30 | 9
> 1950 | 10
> 7 | 11
> 67 | 12
>
> Thanking you in advance for any help on this. The caffiene seems to be not
> working well today.
>
> Aaron
>
>
Do you have a table which lists exhaustively the know activity_id values
in the system. You may need to 'select distinct activity_id from
foo_activity' to get the complete list, then left join against that (or
the existing list) in your count. You need something to supply the 5,6
and 8.

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