在类似记录中选择最新的更新记录

Question

我有2个表段和摘要。
我想按日期间隔列出节目，并仅显示最新的片段（以粗体显示），因为它是该人的片段的最新副本。
这是我以前在下面得到的查询：

select seg.summ, su.channel, seg.block_id, seg.person, seg.updated_at as segupdate 
from segments seg 
   left join summaries su on seg.summ = su.id 
where su.created_at between '2018-06-06' and '2018-07-13' 
order by summ, block_id, seg.updated_at desc;   

我想要这个：

如何更改查询以仅显示加粗的行？删除旧版本的重复项？

Answer 1

您可以尝试使用ROW_NUMBER窗口函数，将行编号设置为order by segupdate DESC，然后获取rn = 1最新数据行。

SELECT * FROM 
(
     SELECT *,ROW_NUMBER() OVER(PARTITION BY summ,channel,block_id,person order by segupdate DESC) rn
     FROM (
        select seg.summ, su.channel, seg.block_id, seg.person, seg.updated_at as segupdate 
         from segments seg 
         left join summaries su on seg.summ = su.id 
         where su.created_at between '2018-06-06' and '2018-07-13' 
     ) t1
) t1
where rn = 1

Answer 2

这就是我所做的：

select distinct on (seg.summ, seg.block_id, seg.person) su.channel, seg.updated_at as segupdate 
from segments seg 
  left join summaries su on seg.summ = su.id 
where su.created_at between '2018-06-06' and '2018-07-13' 
order by summ, block_id, person, seg.updated_at desc;