``` select live_id, max(user_count) max_user_count from ( select user_id, live_id, sum(user_change) over(partition by live_id order by event_time) user_count from ( select user_id, live_id, in_datetime event_time, 1 user_change from live_events union all select user_id, live_id, out_datetime, -1 from live_events )t1 )t2 group by live_id; 同时最大人数问题，打标签+1，-1然后union聚合，结束