htaccess rewrite thoughts

If I want to redirect every instance of and all files/folders

http://mydomain.com

to

http://www.mydomain.com

Would I do this like this?

RewriteEngine On
RewriteCond %{HTTP_HOST} ^mydomain.com [NC]
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [L,R=301]

Is this a good idea from an SEO perspective?

Hello,

yes, the code is correct and this is recommended from SEO point of view.