Using LIKE with indexed column

A Question on Indicies and Like

Environment
Hp 755
Hpux 9.01
Oracle 7

I have a table (45,000+ records) with a varchar2 (60) not null column, col1, with a unique index built on it.

When I select a record and specify a particular value for col1 ( ie select * from table1 where col1 = 'howdy doody time') , I get an answer back in 0.01 seconds. Rather faster that I expected.

When I select a record using like (ie select * from table1 where col1 like 'howdy doody tim%' ) I must wait 60 to 220 seconds for the answer, even though there is only one record in the table that will match.

I figured it would take longer, but I did not expect that kind of increase in processing time.

It the index used to find the record?
What could I do to speed it along?
What exactly does Oracle do? (I love the details, helps me remember things)

Thanks for any input.

Greg Tupper
Saic Comsystems

gtupper_at_nosc.mil Received on Tue Apr 18 1995 - 00:00:00 CEST