Re: - Slow Query

Sorry, it was an error in previous letter.

3 липня 2009 р. 14:22 Віталій Тимчишин <tivv00(at)gmail(dot)com> написав:

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> 2009/7/1 Mike Ivanov <mikei(at)activestate(dot)com>
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>> > LEFT outer JOIN ville ON ville.uid = bien.ref_ville
>> > LEFT outer JOIN freguesia_ville ON freguesia_ville.ref_ville =ville.uid
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>> This is not enough. You have to add this condition as well:
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>> AND bien.ref_ville = freguesia_ville.ref_ville
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>> In other words, when you link three tables by a common field, all three
>> relationships should be explicitly expressed, otherwise you'll have this
>> type of explosive row multiplication.
>>
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> Why so? Is not changing "freguesia_ville.ref_ville =ville.uid" to
> "freguesia_ville.ref_ville =bien.ref_ville" enough (to prevent cases when
> ville.uid is null as result of join)?
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