Re: efficient count/join query - Mailing list pgsql-sql

On Friday 07 Feb 2003 10:48 am, Tomasz Myrta wrote:
> Gary Stainburn wrote:
> > Hi folks,
> >
> > I've got two tables, first a history table containing tallies for
> > staff/jobs prior to going live, and second a roster table showing date,
> > diagram, job with one record per person per job per day.  the tables are:
> >
> > create table history (
> > hsid    int4 not null references staff(sid),
> > hjid    int4 not null references jobs(jid),
> > hcount    int4,
> > primary key (hsid,hjid));
> >
> > create table roster (
> > rodate    date not null,
> > rogid    int4 not null references diagrams(gid),
> > rojid    int4 not null references jobs(jid),
> > rosid    int4 references staff(sid),
> > primary key (rodate, rogid, rojid));
> >
> > What's the best/quickest/cheapest way to create a view in the format of
> > the history table but including the details from the roster table for all
> > records prior to today.
> >
> > I've been looking at some form of sub-select/join scheme but as some will
> > only exist on the history and some will only exist on the roster while
> > many will exist on both.
>
> Hello again.
>
> What if they exists in both tables - you need only one row result?
> If yes, you should use FULL OUTER JOIN and COALESCE.
>
> select
>  coalesce(hjid,rjid) as jid,
>  coalesce(hsid,rsid) as sid,
>  hcount,
>  rodate,
>  rogid
> from
>  history
>  full outer join roster on (hjid=rjid and hsid=rosid)
>
> Using other names for the same field in other tables comes again -
> If you have the same name for jid and sid, you wouldn't need coalesce.
>
> Regards,
> Tomasz Myrta

Hi Tomasz,

I don't think you understand what I mean.

The history table could be thought of as the following SQL statement if the
data had actually existed. This table actually represents a manually input
summary of the pre-computerised data.
insert into history   select rosid, rojid, count(*) from roster_staff group by rssid, rsgsid;

If I have a history of
hsid | hjid | hcount
------+------+--------   1 |    2 |      3   1 |    3 |      1   5 |    5 |      4   6 |    5 |      3   9 |    4 |
4  14 |    5 |      4 

and I have a roster of
 rodate   | rogid | rojid | rosid
-----------+-------+-------+-------
2003-02-15 |   1   |   2   |   1
2003-02-15 |   1   |   5   |   5
2003-02-16 |   1   |   5   |   1

I want my view to show
hsid | hjid | hcount
------+------+--------   1 |    2 |      4   1 |    3 |      1   1 |    5 |      1   5 |    5 |      5   6 |    5 |
3   9 |    4 |      4  14 |    5 |      4 

--
Gary Stainburn
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