Re: Index not used by query

Presuming the system is running in 'CHOOSE' mode

the cost based optimiser works out that the 'cost' of the query by Full Table Scan is cheaper than by index.

Regards

--
Kevin A Lewis (BOCM PAULS LTD - Animal Feed Manufacturer - Ipswich England)

                        <KevinALewis_at_HotMail.com>

The views expressed herein by the author of this document are not necessarily those of BOCM PAULS Ltd. Frank Calfo <fcalfo_at_psateam.com> wrote in message news:01beb34e$41603e40$e401010a_at_FRANK...
> I'm doing a simple test on index usage:
>
> I have a table, Employee, with the columns: empid,
> name,
> type
>
> I have a simple query: select * from employee where type = 4 ;
>
> When I run an execution plan on this statement it indicates that
> Oracle will do a full table scan on the employee table.
>
> This is as expected
>
> I then add a nonunique index to the table consisting of only the type
> column
>
> I run statistics on the schema with the estimate option
>
> Then I rerun the execution plan with this same query
>
> It still indicates Oracle will do a full table scan on the table.
>
> Why won't Oracle use the index?
>
> Thanks.
>
>
Received on Thu Jun 10 1999 - 10:36:41 CDT