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From: Atle <trollet@skynet.be>
Newsgroups: comp.lang.beta
Subject: PostGreSQL - Latest :-)
Date: Fri, 24 Nov 2000 16:01:45 +0100
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Xref: news.cs.au.dk comp.lang.beta:12653

I have had an easy job of interfacing to PostGreSQL over the libpq, and now I see that the interface can be very Beta-like indeed.
What I wanted initially, was something that worked like a Container, and now I see that this might be a kind of ClassificationSet.

I once took a course in dabases, and part of the course was something called the RAS - the Relational Algebra System, the most
powerful I have seen, most, if not all set functions were supported.


JOIN, PROJECT and SELECT could be mixed in any order, actually very Beta-like!

SELECT fa,fb,fc,fd,fe,fg FROM DB giving CB

SELECT fa,fg from CB WHERE fa='criterion' GIVING HB

could be expressed like

SELECT fa,fb FROM (SELECT fa,fb,fc,fd,fe,fg FROM DB) GIVING HB

Now the scan: pattern definitely has a place here ... 

Could this be a possibility?:

'SELECT * FROM SYMPTOMS WHERE s ~* Headache'->PQ.scan(# DO (tupleNo,fieldNo)->getValue->Screen.putText #)

Or should rather the patterns SELECT, PROJECT and JOIN be defined on virtual patterns?

PQ.SELECT(#
	WHERE::<(# DO ((fa > 3000) AND (fa < 35000))->value #);
	fa:@INTEGER; fb:^TEXT
	fb[]->Screen.putLine
#)

I personally like the second one better ... comments?

Thanks, Atle

PS
	BTW, the libpq is similar to ODBC, only a LOT simpler.
/PS