SELECT *
FROM section_user_map
JOIN users USING (UID)
JOIN verification USING (UID)
WHERE SectionID = 65
AND CompleteDate BETWEEN '2012-05-09 12:00:00'
AND '2012-05-11 12:00:00'
See it on sqlfiddle.
No UNION
required. Outer join would only be required if you still want to return results for users who do not exist in one (or both) of the users
or verification
tables.
solved MYSQL: Search for User ID in one table to search for data in 2 other tables, then show data from all 3 tables