Re: Is this JOIN good ?

On Mon, 16 Oct 2006 13:11:50 -0700, DA Morgan <damorgan_at_psoug.org> wrote:

>Charles Hooper wrote:
>> klabu wrote:
>>> Assuming you don't know anything about these 3 tables beyond FK & PK
>>>
>>> select *
>>> from A, B, C
>>> where A.fk = C.pk
>>> and B.fk = C.pk
>>>
>>> Is this JOIN "complete" ?
>>> or an additional predicate is needed between A and B ?
>>
>> Transitive closure:
>> A = C
>> B = C
>> Logic states that this implies that:
>> A = B
>>
>> Perform a 10053 trace, you may see the Cost Based optimizer adding a
>> constraint like this:
>> A.FK = B.FK
>
>Which, if it were true, would indicate a bad design.

 In what way do you believe it indicate this?

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