Creating Indexes on Number Columns

[Deepika Saxena]

Hi,
is there any performance overhead creating indexes on a table columns, whose data type is other than number or interger? i mean if we have a table Emp with the following structure

 Emp{ eno integer, ename varchar(20), salary number(6,2)}

and assume that eno, ename both will only accept unique values. in this case , what is the recommended way to create index? is it on eno or ename? i read that indexes on numbers will have better performance over the indexes, which are created on characters. could any body please explain the reason behind this.
Thanks.
--Deepika

[Jeanne Boyarsky]

Deepika,
The fastest index is the one that is used the most. Do you have more queries/joins by number or name? I would imagine number making it the best choice of an index.