Question

我有一个sql表：

DATE  USER     FLAGGED    COMMAND   
1     Alice    0          sudo gparted   
2     Bob      1          sudo   
3     Bob      0          mv   
4     Alice    1          sudo rm -rf    
5     Charlie  1          sudo chown

我想选择用户的最后标记操作

DATE  USER     FLAGGED    COMMAND    
2     Bob      1          sudo    
4     Alice    1          sudo rm -rf   
5     Charlie  1          sudo chown

我试过

select DATE, USER, REQUEST
from
(

select DATE, USER, REQUEST, FLAGGED
row_number() over(partition by USER order by date desc) rn
from USERDATA
) src
where rn = 1 and FLAGGED = 1

但它总结了鲍勃。我怎么能。添加＆＃34; FLAGGED = 1＆＃34;的正确方法是什么？到SQL请求？

Answer 1

将标记条件移动到子查询，因此只检索标记为= 1的行，您可以选择rn = 1条件的最新行。

select DATE, USER, REQUEST
from
(
select DATE, USER, REQUEST, FLAGGED,
row_number() over(partition by USER order by date desc) rn
from USERDATA
where flagged = 1
) src
where rn = 1

Answer 2

您还可以使用通用MAX查询：

select DATE, USER, REQUEST
from USERDATA
WHERE (date, user) IN (
  select MAX(DATE) as date, USER
  from USERDATA
  where flagged = 1
  group by user
) 
AND flagged = 1

但是，请注意，如果有两个用户条目具有相同的日期是MAX，则可能会返回重复...您可以通过在外部SELECT上使用MIN或MAX来避免这种情况。

Answer 3

此处首先为用户选择最新条目，然后删除未标记的条目。相反，您应首先选择所有FLAGGED条目，然后找到最新的条目。这段代码应该有用。

 select DATE, USER, REQUEST
 from
  (
    select DATE, USER, REQUEST, FLAGGED 
   row_number() over(partition by USER order by DATE desc) rn
    from USERDATA WHERE FLAGGED = 1  
  ) src
 where rn = 1

SQL选择可见

3 个答案: