link_to alphabetical search

Hi all,

I have a link_to method in rails for each letter of the alphabet (early
days yet, will put it in a loop later). I have the same for a console on
another page and that one works fine but the one on my page for the
letters does not.

I have the following in my model:

  def index
     user_relation = case params[:username].present?
  when true then User.where(:username => params[:username])
  else User
  end

    @users = user_relation.paginate :page=>params[:page], :order =>
'created_at desc', :per_page => 10
  end

and this is an example in my index:

<%= link_to 'A', users_path(:username => 'A'), {:style=>'color:#FFFFFF',
:class => "tabel-3"}%>

Now if I click on A it does not return any results despite there being
many users with the letter A but if I was to for example put in the
brackets the name AdrianShaw (one of the users in my database) and click
A it would return that exact user. What it seems to be doing is search
but only for exact match results, anything less than the full word and
it does not return.

How would I go about doing this so that it gets all users with the first
letter A and so on?

Thanks
Christopher Jones