def signup_user
    begin
        ActiveRecord::Base.connection.execute(
            "insert into someTable (column) values ('foo')")        
    rescue Mysql::Error => e
            render_text "oopse!"
    else
            
    end
end

##########################
# in mysql, someTable.column is unique so i get
#  Mysql::Error: Duplicate entry 'foo' for key 2: insert into someTable (column) values ('foo')