apache redirect from non www to www

Question

I have a website that doesn\'t seem to redirect from non-www to www.

My Apache configuration is as follows:

RewriteEngine On
### re-direct t         


        

Answer 1

    ServerAlias example.com
    RedirectMatch permanent ^/(.*) http://www.example.com/$1

This will redirect not only the domain name but also the inner pages.like...

example.com/abcd.html               ==>    www.example.com/abcd.html
example.com/ab/cd.html?ef=gh   ==>    www.example.com/ab/cd.html?ef=gh