题解 | 短视频直播间晚上11-12点之间各直播间的在线人数

SELECT 
    u.room_id,
    r.room_name,
    COUNT(DISTINCT u.user_id) AS user_count
FROM
    user_view_tb u
JOIN room_info_tb r ON u.room_id=r.room_id
WHERE
    u.in_time <= '23:59:59' AND u.out_time >= '23:00:00'
GROUP BY
    u.room_id, r.room_name
ORDER BY
    user_count DESC

统计在线人数时记得去重，COUNT(DISTINCT X)用法