如何删除 Postgres 中的两行重复数据之一？

Question

我正在使用 Postgres 9.5。我有以下查询，旨在在我的 table.

中查找相同的数据行（但 ID 唯一）

select e.name, 
       e.day, 
       e.distance, 
       e.created_at, 
       e2.created_at 
from events e, 
     events e2 
where e.name = e2.name 
  and e.distance = e2.distance 
  and e.day = e2.day 
  and e.web_crawler_id = e2.web_crawler_id 
  and e.id <> e2.id 
  and e.web_crawler_id = 1 
order by e.day desc;

我最终想删除其中一个重复的行——所以也许删除具有最大“created_at”日期的行。但是我不确定如何只对两个相同行中的一个 return 编写查询。我该怎么做？

Answer 1

您可以使用 LIMIT：

select e.name, e.day, e.distance, e.created_at, e2.created_at from events e, events e2 where e.name = e2.name and e.distance = e2.distance and e.day = e2.day and e.web_crawler_id = e2.web_crawler_id and e.id <> e2.id and e.web_crawler_id = 1 order by e.day desc LIMIT 1;

Answer 2

有很多方法，但无需改变您的 sql 太多，您可以做更多而不是 <> for id:

select e.name, e.day, e.distance, e.created_at, e2.created_at 
from events e, events e2
where e.name = e2.name
and e.distance = e2.distance
and e.day = e2.day 
and e.web_crawler_id = e2.web_crawler_id 
and e.id > e2.id 
and e.web_crawler_id = 1

如何删除 Postgres 中的两行重复数据之一？

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