efficient count/join query

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.
--
Gary Stainburn
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