Question

我有一个表格，可以按时间为每个资源更新条目。为简单起见，我们可以说表中有这些必要的列

-resourceid
-entrytime

由于某些原因，在几毫秒内，桌面上有许多资源元素的条目，我想删除已记录的第二个条目。

我通过在表上进行自联接来查找条目来查找这些条目。

select b.resourceid,b.entrytime 
from RESOURCE_DATA_TABLE a 
   join RESOURCE_DATA_TABLE b on a.resourceid=b.resourceid 
where b.collectiontime > a.entrytime 
  and b.entrytime < (a.entrytime + interval '4 millisecond');

但如何一次性删除它们。

Answer 1

如果使用窗口函数来查找行，这会更容易：

error: ``a

现在您可以使用它删除行：

select * 
from (
  select resourceid, entrytime, 
         entrytime - lag(entrytime) over (partition by resourceid order by entrytime) as diff, 
         row_number() over (partition by resourceid order by entrytime) as rn
  from resource_data_table
) t
where diff < interval '4 millisecond';

Answer 2

试试这个

Delete 
FROM RESOURCE_DATA_TABLE r
WHERE 
    EXISTS (

      select * 
      from RESOURCE_DATA_TABLE a 
      join RESOURCE_DATA_TABLE b on a.resourceid=b.resourceid 
      where b.collectiontime > a.entrytime 
      and b.entrytime < (a.entrytime + interval '4 millisecond')
      and b.resourceid = r.resourceid
      and b.entrytime = r.entrytime 

)

或者这个

Delete 
FROM RESOURCE_DATA_TABLE r
WHERE 
    EXISTS (
       Select * from 
      (select b.resourceid,b.entrytime 
      from RESOURCE_DATA_TABLE a 
      join RESOURCE_DATA_TABLE b on a.resourceid=b.resourceid 
      where b.collectiontime > a.entrytime 
      and b.entrytime < (a.entrytime + interval '4 millisecond')
      ) temp 
      where temp.resourceid = r.resourceid
      and temp.entrytime = r.entrytime 

)

删除时间间隔非常小的条目

2 个答案: