Re: how to do this query?

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От Stephan Szabo
Тема Re: how to do this query?
Дата
Msg-id 20030520094321.T68048-100000@megazone23.bigpanda.com
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Ответ на how to do this query?  (ww zz <ts_999@yahoo.com>)
Ответы Re: how to do this query?
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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>;
 



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