Re: Performance question

From: Alexander Costa <alexander_at_ax.apc.org>
Date: Thu, 17 Jun 1999 15:54:08 -0300
Message-ID: <7kbg7a$4rv@ax.apc.org>

Hi Bill,

When you use 'like' with a '%' in the begining of the string you want to find, the SGBD will make a FULL TABLE SCAN, and no indexes will be used.

Alexander Costa

Bill Mann <bill.mann_at_worldtalk.com> wrote in message news:37693C9D.33F982EE_at_worldtalk.com...
> Can anyone comment on the performance of the following select statement
> when most of the rows in the table will contain NULL values for the
> "hobbies" varchar2(1024) column.
> The "hobbies" will be a string with the following format
> "football:hockey:cricket..."
> I already know that this type of search is slow since Oracle needs to
> scan the string completely. Since most rows are NULL, will Oracle still
> walk thru each row ? Is it worth indexing the someinfo column, to stop
> Oracle from checking rows containing Nulls ?
>
> THanks,
> Bill
>
> SELECT name from employee
> where
> hobbies like '%football%'
>
>
Received on Thu Jun 17 1999 - 13:54:08 CDT