Hello,

I understand the concept of using index, however there are some few things
that I haven't yet grasp.

1) Creating an index on 2 or more columns, helps the query in what way?
eg) I have a table inventory where I can search by itemid or
description.
I can create an index for itemid and another index for description
to speed up searching for each column.
Now what would an index on both itemid and description serve?

2) Making the index unique impacts the index in what way?

thanks