Обсуждение: RE: [HACKERS] Re: Informix and OUTER join syntax

I was under the impression that if you used NATURAL JOIN, then the join
would be made on the declared keys.

Or doesn't SQL92 support declared keys?

MikeA

-----Original Message-----
From: Thomas Lockhart
To: Don Baccus
Cc: Bruce Momjian; PostgreSQL-development
Sent: 00/01/14 05:14
Subject: Re: [HACKERS] Re: Informix and OUTER join syntax

> And if I understand SQL92 correctly, if tab1, tab2, and tab3 only
> share col1 in common, then you can further simplify:
> SELECT *
> FROM tab1 NATURAL RIGHT JOIN (tab2 NATURAL RIGHT JOIN tab3)
> Is that right? ...and some
> might argue this is less clear than explicitly listing the column(s)
> to join on.

But this is "natural", right? ;)
                 - Thomas

-- 
Thomas Lockhart                lockhart@alumni.caltech.edu
South Pasadena, California

************

> I was under the impression that if you used NATURAL JOIN, then the join
> would be made on the declared keys.

Nope. On column names in common.
                - Thomas

-- 
Thomas Lockhart                lockhart@alumni.caltech.edu
South Pasadena, California

At 03:20 AM 1/15/00 +0000, Thomas Lockhart wrote:
>> I was under the impression that if you used NATURAL JOIN, then the join
>> would be made on the declared keys.
>
>Nope. On column names in common.

(phew!)  This is how I remembered it.  Though it's in Boston and I'm
in Portland (OR, that is), due to my space-headedness, I can strongly 
recommend that interested folks spend some of those $25,000 or so
dollars saved by not using Oracle on a copy of Date's SQL primer :)

(I forget the exact title, but it's pretty good.  I'll probably pick
up the standard, too, but Date's book is as much critique as explanation
and the SQL 92 standard seems in need of critical comments)



- Don Baccus, Portland OR <dhogaza@pacifier.com> Nature photos, on-line guides, Pacific Northwest Rare Bird Alert
Serviceand other goodies at http://donb.photo.net.
 

Don Baccus wrote:

> At 03:20 AM 1/15/00 +0000, Thomas Lockhart wrote:
> >> I was under the impression that if you used NATURAL JOIN, then the join
> >> would be made on the declared keys.
> >
> >Nope. On column names in common.
>
> (phew!)  This is how I remembered it.  Though it's in Boston and I'm
> in Portland (OR, that is), due to my space-headedness, I can strongly
> recommend that interested folks spend some of those $25,000 or so
> dollars saved by not using Oracle on a copy of Date's SQL primer :)
>
> (I forget the exact title, but it's pretty good.  I'll probably pick
> up the standard, too, but Date's book is as much critique as explanation
> and the SQL 92 standard seems in need of critical comments)
>
> - Don Baccus, Portland OR <dhogaza@pacifier.com>
>   Nature photos, on-line guides, Pacific Northwest
>   Rare Bird Alert Service and other goodies at
>   http://donb.photo.net.
>
> ************

IMHO "A Guide to THE SQL STANDARD" by Date/Darwen is an interesting
documentation but I'm reading
another very, very interesting book about SQL, here the title in english:
"SQL: The Standard Handbook" (Based on the New SQL Standard ISO 9075:1992(E)
by Stephen Cannan and Gerard Otten.
This a clear explanation of SQL standard made by two persons that colaborated
direct or indirect to establish
such Standard.

José