在SQL中按行划分

Question

这是我的桌子

Guid是唯一的。一个guid仅与一个用户相关联。差异用户将没有相同的guid。在这里，我希望所有上校都像Userid, guid, status, Errorcode and Retry。我想从表中提取所有记录，其中该guid的重试次数最大。

赞

该guid的重试可以是0或1或2。

我的查询：

SELECT
  Userid,
  Guid,
  Status,
  ErrorCode,
  Retry,
ROW_NUMBER() OVER(PARTITION BY Userid, Guid ORDER BY Retry) AS Row_Number
FROM UserInfo

如果我输入Row_Number=1，该guid只会获得第一。 我想为此guid选择最大重试记录。

Answer 1

ROW_NUMBER实际上应该在这里起作用，但是您需要在通话中使用ORDER BY Retry DESC：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY userid, Guid ORDER BY Retry DESC) rn
    FROM UserInfo
)

SELECT userid, Guid, Status, ErrorCode, Retry
FROM cte
WHERE rn = 1;

如果您使用的是SQL Server，则实际上我们甚至可以不使用正式的子查询来编写查询：

SELECT TOP 1 WITH TIES userid, Guid, Status, ErrorCode, Retry
FROM UserInfo
ORDER BY ROW_NUMBER() OVER (PARTITION BY userid, Guid ORDER BY Retry DESC);

Answer 2

这是您的查询，不需要用户row_number，MAX()将解决此问题。

select t2.userid, t2.Guid, t2.Status, t2.ErrorCode, t1.maxRet from 
UserInfo
inner Join
(select 
 max(Retry) AS maxRet, userid, Guid
from UserInfo
Group by userid, Guid) as t1
on t1.Guid = t2.Guid and t1.userid = t2.userid

Answer 3

使用ORDER BY Retry desc

select * from
(
select userid,Guid,Status,ErrorCode,Retry,
ROW_NUMBER() OVER(Partition by userid,Guid ORDER BY Retry desc) AS Row_Number
from UserInfo
)A where Row_Number=1