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Help to Speed up SQL
Message
De
09/03/2002 16:44:15
Mike Yearwood
Toronto, Ontario, Canada
 
 
À
09/03/2002 13:10:07
Bill Morris
Morco
Barstow, Californie, États-Unis
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Titre:
Re: Help to Speed up SQL
Divers
Thread ID:
00629818
Message ID:
00630636
Vues:
28
Hey Bill

Select FieldList, sum(Field1) ;
from t1 ;
where not in (select from t2) ;
group by Field3

Doesn't it seem cleaner to exclude the aliases. I only include them when I need to to prevent confusion. The not in may speed things up. Please let me know.

Thanks

>>Hilmar,
>>
>>I've discovered something else. This probably isn't a Rushmore problem after all.
>>I'll start here before starting another thread.
>>
>>Here's my original SQL that got the job done, but was slow.
>>I always made sure that t1 and t2 were open before the SQL was executed.
>>I'm working on it now on a stand alone machine (no network).
>>
>>Select t1.FieldList, sum(t1.Field1) ;
>>  from t1 left join t2 ;
>>  on t1.<SameField> = t2.<SameField> ;
>>  where !t1.Field2 ;
>>  group by t1.Field3
>>  having isnull(t2.<SameField>)
>>
>>I've discovered that it only runs slow the first time (whether from the command window or a prg). As much as 36 seconds depending on what else is open on the computer. If I run it again (in the command window hit UPARROW and ENTER, it runs fast. As fast as 1.6 seconds.
>>
>>Also, if I switch windows in Windows 98 (say to my browser) and switch back to VFP, then hit UPARROW and ENTER it runs slow again. I don't do anything in the browser, just switch windows and back again.
>>
>>I've tried finding another query that behaves similarly, but I can't find any. (I've only spent about 5 minutes so far). They always run within 5% or so of the original speed (as long as the tables are open already).
>
>I've just discovered something else.
>I had 2 fields in each table that were filled with bintoc(fk1) + bintoc(fk2,1). I was going to start using them as SameField. I removed them and the problem got better. Still didn't go away, but got better.
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