Re: query problem - get count in related table - Mailing list pgsql-novice

From Rory Campbell-Lange
Subject Re: query problem - get count in related table
Date
Msg-id 20020523231458.GA15332@campbell-lange.net
Whole thread Raw
In response to Re: query problem - get count in related table  (Ron Johnson <ron.l.johnson@cox.net>)
Responses Re: query problem - get count in related table
Re: query problem - get count in related table
List pgsql-novice
Hi Ron

Thanks very much for your mail - apologies for the vagueness of my
original query. Your snippet works pretty well (although a.data has to
be specified in the group by, it appears). However I'm still looking to
get a result like this:

         id | data | count
        ----+------+-------
          1 |    2 |     3
          2 |    1 |     2
          3 |    4 |     1
          5 |    2 |     0
        (3 rows)

Cheers!
Rory

------------------------------------------------------------------
progress so far:

brandf=# select * from a;    brandf=# select * from b;
 id | data                    id
----+------                  ----
  1 |    2                     2
  2 |    1                     2
  3 |    4                     1
  5 |    2                     1
(4 rows)                       1
                               3
                             (6 rows)


brandf=# select a.id, a.data, count(*) from a,b where b.id = a.id
         group by a.id, a.data;

         id | data | count
        ----+------+-------
          1 |    2 |     3
          2 |    1 |     2
          3 |    4 |     1
        (3 rows)


On 23/05/02, Ron Johnson (ron.l.johnson@cox.net) wrote:
> Your email is pretty vague, but maybe this is what you want:
>
> select a.id, a.data, count(*) as cnt
> from a, b
> where b.id = a.data
> group by a.id = a.data;

> On Thu, 2002-05-23 at 12:31, Rory Campbell-Lange wrote:
...
> > I'd like to run a query that returned the following results:
> >
> >  a.id  a.data  count(b.id where b.id = a.data)
> >  ---------------------------------------------
> >  1     2       2
> >  2     1       3
> >  3     4       0
--
Rory Campbell-Lange
<rory@campbell-lange.net>
<www.campbell-lange.net>

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