Find last record updated

I always get confused when I have to make a search with Active Record
a little beyond the most ordinaire. How do I find the record that was
updated the last?
It has to be something like

Ad.find :conditions => updated_at = :last

I just don't know how to code it.

Ad.find :first, :order => "updated_at DESC", :limit => 1

cheers,
bartz

Does this work?

  Ad.find(:first, :order => "updated_at DESC")

Thanks Roy and Bart. Both sentences work and return the same record.

Abel wrote:

I always get confused when I have to make a search with Active Record
a little beyond the most ordinaire. How do I find the record that was
updated the last?
It has to be something like

Ad.find :conditions => updated_at = :last

How about
Ad.find :first, :order => 'updated_at DESC'