2 Quick SQL Questions: Paginate Conditions and Adding to Val

I have 2 quick SQL questions that all my googling couldnt come up with
an answer

  1. Paginate results based on 2 conditions

I currently have sorthelper sorting based on title/author. I’d like
the option to select based on 3 genres then be able to sort that
through those results by title. I haven’t be able to see how to handle
sorting with a variable condition. (codes below

  1. How to add to current value

How would I add to a current value in my table?

value = value.current + value.new

def upcoming

items_per_page = 8
@total = Albums.count
@sorter = SortingHelper::Sorter.new self, %w(artist album
votes_count date created_at), @params[‘sort’], @params[‘order’],
‘created_at’, ‘asc’
@albums_pages, @albums = paginate :albumss, :order =>
@sorter.to_sql, :per_page => items_per_page

render :layout => ‘albums_upcoming’