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How can I optimize this query?
Message
 
À
31/01/2005 03:21:12
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 8 SP1
OS:
Windows XP SP2
Database:
Visual FoxPro
Divers
Thread ID:
00982000
Message ID:
00982218
Vues:
47
Thanks I'll rembember that.
>>>With 22K records into the outer table, the expected time for your select is max 100ms.
>>>
>>>Fabio
>>
>>Fabio,
>>
>>If you don't mind for jumping in, how did you calculate the expected time or in general how do you ecalculate the expected for a query.
>>
>>TIA.
>
>From the experience.
>However, if:
>- the records count returns from the SELECT is one small fraction of the cartesian product of "select tables"
>- the dimension of the final record is of 100-300 bytes
>- the select where and join are optimized
>- the "select tables" are cached
>- the PC is of class 1 - 2 GHz
>
>then can be estimated an exec time to the :
>MAX(RECCOUNT("select tables"))/(100000..500000) seconds
>
>Of course some exceptions exist, but normally this estimation is a upper bound.
>
>Fabio
Zakaria al Azhar
My blog on Actuaris.net
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