On Jun 30, 2009, at 4:14 AM, Waldemar Bergstreiser wrote:
>> I don't get it either. by *= do you mean the Oracle-style outer
>> join?
>> in which case why is this not just
>>
>> select * from a,
>> left outer join b on (a.b_id = b.id)
>> left outer join c on (b.c_id = c.id)
>> left outer join d on (a.d_id = d.id)
>> left outer join f on (d.f_id = f.id)
>>
<snip>
>
>>> select * from a left outer join b on (a.b_id=b.id) ....
>>>
>>> But I don't see any clear way to specify that table C should be
>>> outer joined only if we got a row from table B.
>>
>> Well that would be the default since if you get no row from b b.c_id
>> will be null.
>>
>
> and if I have a row in table C where c.id is null? A don't know.
No, it's perfectly clear as 'NULL = NULL' evaluates to false:
postgres=# select null = null;
?column?
----------
(1 row)
Erik Jones, Database Administrator
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