重写SQL查询以与Laravel查询生成器一起使用

Question

$query = "SELECT *, (id.number_of_candidates - t.counted) as available 
    FROM interview_dates id 
    LEFT JOIN (SELECT interview_dates_id,COUNT(interview_dates_id) as counted 
        FROM date_timeslot GROUP BY interview_dates_id) as t 
    ON t.interview_dates_id=id.id 
    WHERE id.number_of_candidates > t.counted";

请帮我用Laravel Query Builder重写一遍。