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Re: Select count(*)

From: Thomas Kyte <tkyte_at_oracle.com>
Date: 6 Jul 2002 06:21:20 -0700
Message-ID: <ag6qsg02gau@drn.newsguy.com>


In article <72954535.0207051011.1058d2be_at_posting.google.com>, calberto2312_at_hotmail.com says...
>
>Hi,
>
> I have two tables (A and B), with the same structure, but in
>different tablespaces. One (A) has 50 million records and was created
>by the other one (B) (by INSERT ... SELECT ....), with 100 million
>records. After the data load, the indexes were created and 'analyze
>compute' executed. Then, after I made some performance tests, the
>results seem very strange :
>
>Test 1 :
>
>set timing on;
>
>select <columns>, ....
>from A, B
>where <indexed_column> = ....
>
>Table B is faster, although it has the double of records. As more
>times this SQL is executed, the time of execution of both tables are
>almost the same.
>
>
>Test 2 :
>
>set timing on;
>
>select count(*)
>from A, B
>where <indexed_column> = ....
>
>Table A is faster.
>
>
>Test 3 :
>
>set timing on;
>
>select count(*) from A, B
>
>Table A is faster.
>
>
> Why table A is just faster when I run select count(*)? Im using
>Oracle 8.0.6.0.0.
>
>Thanks in advanced,
>Carlos

I have no idea what you might mean by "table A is faster" or "table B is faster" since you use both A and B in all queries. Makes no sense....

--
Thomas Kyte (tkyte@oracle.com)             http://asktom.oracle.com/ 
Expert one on one Oracle, programming techniques and solutions for Oracle.
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Received on Sat Jul 06 2002 - 08:21:20 CDT

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