Question

这是查询：

ActiveRecord :: StatementInvalid（PGError：错误：语法错误处于或接近“over” select *，rank（）over（thread_i分区... ^

     SELECT *
     FROM (                                                                  
             select *, rank() over (partition by thread_id order by created_at DESC)
             from posts
             where circle_id IN (134) OR (receiver_id=3)
           ) as dt
     WHERE rank = 1

编辑：这里是我要做的详细解释： Rails 3 app with PostgreSQL - Getting the list of messages grouped by converstation

事实证明，Heroku共享DB是一个PostgreSQL版本8.3，因此没有Windows函数，所以问题变成如何在PostgreSql 8.3中进行此查询？

谢谢！

Answer 1

试

SELECT p.*
 FROM (                                                                  
         select x.thread_id, max(x.created_at) as maxdt
         from posts x
         where x.circle_id IN (134) OR x.receiver_id=3
         group by x.thread_id
       ) as dt
 INNER JOIN posts p ON p.thread_id = dt.thread_id and p.created_at = dt.maxdt 
 ORDER BY p.created_at DESC

编辑 - 根据评论：

SELECT p.*
 FROM (                                                                  
         select x.thread_id, max(x.created_at) as maxdt, max (OID) maxo
         from posts x
         where x.circle_id IN (134) OR x.receiver_id=3
         group by x.thread_id
       ) as dt
 INNER JOIN posts p ON p.thread_id = dt.thread_id and p.created_at = dt.maxdt AND p.OID = dt.maxo
 ORDER BY p.created_at DESC

Answer 2

这应该可以帮助你：

 SELECT p.*
 FROM (                                                                  
         select thread_id, max(created_at) as maxdt
         from posts
         where circle_id IN (134) OR (receiver_id=3)
       ) as dt
 INNER JOIN posts p ON p.thread_id = dt.thread_id and p.created_at = dt.maxdt

PostgreSQL查询在本地工作但不在Heroku上（相同的数据）

2 个答案: