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Re: Select count(*)

From: Carlos Alberto <calberto2312_at_hotmail.com>
Date: 8 Jul 2002 07:54:54 -0700
Message-ID: <72954535.0207080654.57d75337@posting.google.com>


Hi Tom,

   Im not using both tables in queries, Im using one table and comparing the execution time with the other table. The SQLs are the same, the only difference is the table in the FROM clause.

Regards,
Carlos

Thomas Kyte <tkyte_at_oracle.com> wrote in message news:<ag6qsg02gau_at_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....
Received on Mon Jul 08 2002 - 09:54:54 CDT

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