help with query - how to limit SELECT to 20

[David Bahar]

SELECT * FROM logbooks WHERE person_id = #{person_id.to_s} AND logbook_type_id = 2 ORDER BY created_at DESC LIMIT 25 UNION ALL SELECT * FROM logbooks WHERE person_id = #{person_id.to_s} AND logbook_type_id = 1 ORDER BY created_at DESC

Seems mysql won't let me put a "order by" on the first select. is there a more efficient way for me to write this query that will let me limit the results to the newest 20 "created_at" records?

Thanks in advance!