Writing queries and trying to do GROUP BY of the LEFT OUTER JOIN, might give you a headache such as “group by is not allowed”.
If this is the case for you try something like this. MAX(..) can be replaced witrh the other functions that works for you.
Might not be the best from perfomance point of view but works.
SELECT q.question, q.question_id, a.answer FROM questions q LEFT OUTER JOIN ( SELECT answer, question_id FROM answers WHERE answer_date > .... AND groupby_column = ( SELECT MAX(groupby_column) FROM answers WHERE question_id = q.question_id ) ) a ON a.question_id = q.question_id WHERE .... ORDER BY ....