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 likeselect * from sample left outer join make using (sid) left outer join measure using
(sid) left outer join result using (rid)where sid=<value>;
