| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jaime Casanova <systemguards(at)gmail(dot)com> |
| Cc: | David Rio Deiros <driodeiros(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org, is04607(at)salleurl(dot)edu |
| Subject: | Re: swap relations to be able to execute a left join |
| Date: | 2005-12-09 17:47:19 |
| Message-ID: | 29660.1134150439@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Jaime Casanova <systemguards(at)gmail(dot)com> writes:
> On 12/9/05, David Rio Deiros <driodeiros(at)gmail(dot)com> wrote:
>> I am sure there is a good reason why you have to swap the relations
>> in PostgreSQL. Anyone?
> Because PostgreSQL is not broken...
> What i see in this SELECT is an LEFT JOIN between AT and U (note that
> the other relations in the FROM are separated by commas so they have
> nothing to do with LEFT JOIN) and is using a JOIN clause from a
> relation that has nothing to do with the LEFT JOIN...
Right. MySQL apparently thinks that JOIN has the same precedence as
comma in a FROM-list, but anyone who has bothered to read the SQL
standard knows that JOIN is supposed to bind tighter than comma.
Your coworker is depending on a flat-out-incorrect behavior of MySQL.
regards, tom lane
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