another question is:
if I do left outer join on a few big tables, will it
be very slow?
--- Stephan Szabo <sszabo@megazone23.bigpanda.com>
wrote:
> On Tue, 20 May 2003, ww zz wrote:
>
> > New to sql and may be a simple question for you:
> >
> > I have four tables
> >
> > sample: sid, sname
> > make: sid, mdate
> > measure: sid, mdate, rid
> > result: rid, resultdata
> >
> > for a gaven sample it always has a sid and sname,
> but
> > it may or may not have any entries in the other
> > tables, the sample could be measured more than
> once
> > and each measure give a result row.
> > question:
> > how do I do a query that given a sid, it will
> retrieve
> > all the information available in the four tables,
> if
> > there are available. If, for example, all tables
> have
> > some entry for a gave sample it will retreve all
> the
> > information, if the "measure" and "result" are
> empty
> > for that sample it will give only the 'sample' and
> > 'make' information....
>
> Well, you're not going to get a limited column set,
> but you can
> get NULLs in the non-applicable table columns by
> using outer joins.
>
> Maybe something like something like
> select * from
> sample left outer join make using (sid)
> left outer join measure using (sid)
> left outer join result using (rid)
> where sid=<value>;
>
>
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