You can use custom SQL statements with the existing database API by creating a subquery specified via the `tables` parameter of `extra`. (This has only been tested with MySQL and may not work with all database back-ends.)
This is a method from the custom manager for the Snippet model used on this site; the basic idea is to be able to ask for the top `n` "foo", where "foo" is something related to Snippet. For example, you can use `top_items('tag')` to get the top Tags ordered by how many Snippets are associated with them. I have a feeling that I could get this down to one query, but haven't yet put in the time for it.
2 snippets posted so far.