Re: efficient count/join query

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.

selectcoalesce(hjid,rjid) as jid,coalesce(hsid,rsid) as sid,hcount,rodate,rogid
fromhistoryfull 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