Doubt in Index

Hi EverB,

I have created a table say T1 with 5 columns (col1.....col5).
I have created an index on col4 and col5.

iam executing a select query say.

select col1,col2,col3 from t1 where col1 =0;

In the above query i hav not used the columns for which i hav created the index.My ques is-

Does the index really works when u execute the above query?

Any answer please.......
It wuld be better if u culd suggest some sites for this.

Thanks and Regds,
Arunno, for that query, the index is ignored

a good tutorial is Optimizing your MySQL Application (http://www.sitepoint.com/print/optimizing-mysql-application) even if you're using something other than mysql