> can i read/save with ruby the columns involved in that SQL select?
If you use Sequel you can retrieve the columns for arbitrary SQL like
this:
require 'sequel/mysql' # assuming you're using MySQL
DB = Sequel('mysql://localhost/mydb')
DB['select * from items'].columns #=> [:id, :name, ...]
But if you're already using Sequel why not construct your queries
using Ruby instead of SQL, e.g.:
dataset = DB.query do
from :items
where {:name =~ /^abc/ &&

rice < 100}
order_by :name
end
p dataset.columns
dataset.each {|r| p r}
You can find more information about Sequel here:
http://code.google.com/p/ruby-sequel
And you can also get help on Sequel-talk:
http://groups.google.com/group/sequel-talk
best
Sharon