| From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
|---|---|
| To: | Sam Mason <sam(at)samason(dot)me(dot)uk> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Multiple natural joins |
| Date: | 2009-03-20 08:32:13 |
| Message-ID: | 49C3548D.3080002@gmx.net |
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| Lists: | pgsql-general |
Sam Mason wrote:
> On Thu, Mar 19, 2009 at 04:22:56PM +0200, Peter Eisentraut wrote:
>> Joins nest from left to write, so
>>
>> tbl_c NATURAL JOIN tbl_a NATURAL JOIN tbl_b
>>
>> means
>>
>> (tbl_c NATURAL JOIN tbl_a) NATURAL JOIN tbl_b
>>
>> If you want a different order, you can set the parentheses differently,
>> with possibly different results.
>
> When would you get different results? As far as I can tell, for INNER
> joins, you'd always get the same thing back for any ordering. With
> OUTER joins it obviously matters what's going on, but that's expected.
Right.
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