Re: relational calculus

From: Malcolm Dew-Jones <yf110_at_vtn1.victoria.tc.ca>
Date: 11 Mar 2009 12:15:19 -0700
Message-ID: <49b80dc7$1_at_news.victoria.tc.ca>

ddf (oratune_at_msn.com) wrote:

: On Mar 10, 6:05=A0am, miten.me..._at_morganstanley.com wrote:

: > Hi,
: >
: > can one tell me how would we write down relational calculus query for
: > one in which we have group by and having clauses ?
: >
: > Regards,
: >
: > Miten.
: > miten.me..._at_morganstanley.com
: > imi..._at_yahoo.com

: I, for one, do not understand your question. Please rephrase.

Perhaps he means the logic predicate type notation, an example expression stolen from Wikipedia...

	{ t : {name} | . s : {name, wage}
	  ( Employee(s) . s.wage = 50.000 . t.name = s.name )
	}

There are various such "mathematical/logical" ways of writing set expressions that correspond to what a relational database does.

I would guess he wants to figure out how to write group by or having using some such notation.

$0.10 Received on Wed Mar 11 2009 - 14:15:19 CDT