求大神幫我把這段原生SQL語句轉成TP5的謝謝！就是Db::('name')->這種鏈式操作的'select a.id, a.title,a.create_time,a.is_solve,count(b.qid) as answer_count from fa_question a,fa_answer b where a.id=b.qid and a.is_solve=0 group by b.qid order by answer_count DESC LIMIT 6';