Getting repeated data

[Anon]

I have a table with several fields:
id, ref, ...

id is auto_increment
ref is varchar 255

The point is to get all the ocurrences where the field ref is repeated. I mean to recover ONLY the registries where the value of ref is repeated somewhere in the table.

Is that posible with SQL only, or should I make a PHP script to process it?

I'm using PHP 4 and MySQL.

Thanks

[Anon]

select ref,count()
from sploshSeveralCansOfYoughurt
group by ref
having count() > 1