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Selecting records from two different tables in one query
Message
De
30/06/2010 09:47:12
Cetin Basoz
Engineerica Inc.
Izmir, Turquie
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
01454516
Message ID:
01471068
Vues:
49
>>>>>I'll try later - busy with work right now. I tried on the tables I had in my test database (in SQL Server).
>>>>
>>>>Ok I just tried for you:
>>>>
>>>                                                    t6   t5   t4   t3   t2   t1
>>>>Client processing time         0    0    0    0    0   16 
>>>>Total execution time        2328 2296 3046 2250 2328 5937 
>>>>Wait time on server replies 2328 2296 3046 2250 2328 5921 
>>>>
>>>>
>>>>Two passes. t1,4 (LEFT), t2,5 (NOT IN), t3, 6 (Exists).
>>>>Cetin
>>>
>>>In your tests performance of the LEFT JOIN seems to be much worse than others. What are tables metrics and how many records did you get as a result of a query? Also, did you discharge the results or not?
>>
>>Yes as I told you before it was the slowest. Metric is simple. 2 million records table created, and copied onto another (structure was as simple as it can be, an ID plus a varchar data field. With a more complex structure it is likely it would be much slower). Then a few more records are added to one of them. Index created on join field.
>>Cetin
>
>Just want to share this link http://sqlinthewild.co.za/index.php/2010/04/27/in-exists-and-join-a-roundup/ that contains performance results for
>IN/EXISTS/INNER JOIN and NOT IN/NOT EXISTS/LEFT JOIN by Gail Shaw.

Thanks but I don't remember I asked for a link. Why would you share it especially when nothing in it that contradicts what I have said.
Cetin
Çetin Basöz

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