Which is more appropriate from a user centric design for html search input.

Say I wanted to allow users to search on account numbers with the following format. 0000-00-0000

Is is better to have a single field for entry [___________________]

or is it better to create 3 text boxes and have the user enter only the numbers? where the dashes are presented on the page

[___] - [__] - [__]

I already have my own opinion. Which approach is more user friendly?

Also, i want to enhance this with begins with and partial matches in the future.