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From "Antonio Gallardo" <agalla...@agsoftware.dnsalias.com>
Subject Re: [ESQL] Improvement....
Date Sat, 25 Jan 2003 22:36:41 GMT
Torsten Curdt dijo:
>> WHAT IS WRONG?
>>
>> In example A all is OK.
>>
>> In example B we are not using the power of the Database Manager.
>>
>> WHY?
>>
>> The LIMIT clause was designed to tell the database engine:
>>
>> "Let find just X rows", then the database engine when it got the X
>> rows stop searching and return the X rows. It improves the response
>> time, since does not to continue searching!
>>
>> Now think in a 10 million row table and YOU KNOW you need only 5 rows!
>
> whether 10 million rows or not - the current sollution will only ask for
>  6 - one additional row. Is that the time penalty you are talking about?

Yes, because you already know that there are only 5 rows for every
register. Then the database will search the last 6th row that no exist.
Forcing to searh in the ENTIRE table.

Maybe your 5 rows are at the beginning of the table but the non existent
6th row will force the Database Engine to search for this.

Antonio Gallardo.
> --
> Torsten
>
>
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