Re: Tutorial D with + restrict
From: Strider <Anymore_at_short.int>
Date: Thu, 30 Mar 2006 14:11:14 +0200
Message-ID: <Xns979690520D71strider5athome_at_195.34.135.101>
>
> It appears to be a join of
> select sno, count(*) as np from sp group by sno
> with
> select sno from s
> on sno
>
Date: Thu, 30 Mar 2006 14:11:14 +0200
Message-ID: <Xns979690520D71strider5athome_at_195.34.135.101>
>
>> WITH ( SP RENAME ( SNO AS X ) ) AS R : >> EXTEND ( S { SNO } ) ADD ( COUNT ( R WHERE X = SNO ) AS NP )
>
> It appears to be a join of
> select sno, count(*) as np from sp group by sno
> with
> select sno from s
> on sno
>
Yes that is exactly what i have thought.
> What RESTRICT ? I see WHERE in the scope of EXTEND in there.
Yes EXTEND is a keyword here, you have given me right direction, thank you.
EXTEND A ADD exp AS Z is a relation with:
...
A body consisting of all tuples t such that t is a tuple of A extended with
a value for attribute Z that is computed by *evaluating* exp on *that*
tuple of A.
Thank you. Received on Thu Mar 30 2006 - 14:11:14 CEST