From: | Don Baccus <dhogaza(at)pacifier(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Planner drops unreferenced tables --- bug, no? |
Date: | 1999-09-29 15:21:58 |
Message-ID: | 3.0.1.32.19990929082158.00a563d0@mail.pacifier.com |
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Lists: | pgsql-hackers |
At 10:34 AM 9/29/99 -0400, Tom Lane wrote:
>play=> select x.f1 from x, x as x2;
>f1
>--
> 1
> 2
> 3
>(3 rows)
>
>It seems to me that the latter query must yield 9 rows (three
>occurrences of each value) to satisfy the SQL spec. The spec defines
>the result of a two-query FROM clause to be the Cartesian product of the
>two tables, period. It doesn't say anything about "only if one or more
>columns of each table are actually used somewhere".
AFAIK, this is correct. For the heck of it, I tried it in
Oracle, and indeed the full cartesian product's returned:
SQL> select x2.i from x, x x2;
I
----------
1
1
1
2
2
2
3
3
3
9 rows selected.
>play=> select count(1) from x;
>count
>-----
> 1
>(1 row)
Again, Oracle 8:
SQL> select count(1) from x, x x2;
COUNT(1)
----------
9
SQL>
- Don Baccus, Portland OR <dhogaza(at)pacifier(dot)com>
Nature photos, on-line guides, Pacific Northwest
Rare Bird Alert Service and other goodies at
http://donb.photo.net.
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