order by 多条件查询 case when

     场景：在按照条件查询后，排序按照不同的条件排序，以及同一个条件 正序和倒序排序。可以考虑使用。

      遇到的排序条件：按照直播的状态，根据条件排序。直播的状态包括：直播、置顶、预告、回放、过期预告。排序条件为：多直播按照 开始时间倒序排序，置顶按照置顶时间正序排序，预告按照离当前时间越近的倒序排序，回放按照开始时间倒序、过期预告按照离当前时间越近正序排序。

     sql语句为：

          

SELECT 
    l.id,
    l.title,
    l.description,
    l.picture,
    l.is_dist_public,l.pre_start_time,
   l.create_time,
    (
        CASE
        WHEN l.live_status = 'NOTICE' THEN
            date_format(
                l.pre_start_time,
                '%Y-%m-%d %H:%i:%s'
            )
        ELSE
            date_format(
                l.start_time,
                '%Y-%m-%d %H:%i:%s'
            )
        END
    ) start_time,
  r.top_time,
    l.category,
    l.live_status,
    l.create_user,
    l.zm_account_id,
    l.source,
    (
        CASE
        WHEN l.live_status = 'LIVING' THEN
            1
        WHEN (
            r.is_top = 1
            AND l.live_status <> 'LIVING'
        ) THEN
            2
        WHEN l.live_status = 'NOTICE'
        AND pre_start_time >= now() THEN
            3
        WHEN l.live_status = 'NOTICE'
        AND pre_start_time < now() THEN
            5
        WHEN l.live_status = 'PLAYBACK' THEN
            4
        END
    ) AS sort,
    r.is_top
FROM
    live l
LEFT JOIN live_zm_account_rel r ON r.live_id = l.id
AND l.live_status != 'PRE_LIVE'
 WHERE
    1 = 1
AND r.is_enabled = 1
AND r.is_delete = 0
AND l.is_enabled = 1
AND l.is_delete = 0
AND r.zm_account_id = '9f7aa1cec50e4b368e69c4f5c14c3fcf'
ORDER BY
    sort ASC, CASE WHEN sort = 1 then l.start_time   END DESC,
     
            CASE WHEN sort = 2 then  r.top_time    END DESC,
            
            CASE WHEN sort = 3 then l.pre_start_time   END ASC,

            CASE WHEN sort = 4 then l.start_time   END DESC,
 
            CASE WHEN sort = 5 then l.pre_start_time   END DESC

LIMIT 15

    CASE when  then  注意一点：后面的排序条件就是 你最终的排序条件。