Question

我有一个看起来像这样的表：

╔════════════╦═════════╦═══════════╗
║ Machine_ID  ║ User_ ID ║ User_Role  ║
╠════════════╬═════════╬═══════════╣
║ Mach_001    ║ N00001   ║         3  ║
║ Mach_001    ║ N00001   ║         4  ║
║ Mach_001    ║ N00002   ║         3  ║
║ Mach_001    ║ N00002   ║         2  ║
║ Mach_002    ║ N00001   ║         3  ║
║ Mach_002    ║ N00002   ║         3  ║
╚════════════╩═════════╩═══════════╝

我正在尝试为每个User_Role - Machine_ID获取最高User_ID的行：

╔════════════╦═════════╦═══════════╗
║ Machine_ID  ║ User_ID  ║ User_Role  ║
╠════════════╬═════════╬═══════════╣
║ Mach_001    ║ N00001   ║ 4          ║
║ Mach_001    ║ N00002   ║ 3          ║
║ Mach_002    ║ N00001   ║ 3          ║
║ Mach_002    ║ N00002   ║ 3          ║
╚════════════╩═════════╩═══════════╝

我该怎么做呢？根据我的数据，我可能会有许多Machine_ID - User_ID个重复项，其中Role级别不同，但我只是喜欢最高级别的角色。

编辑：根据Gordon Linoff的回答，我得到了我想要的东西：

SELECT Machine_ID, User_ID, User_Role
FROM (SELECT ex_rt.*,
        row_number() OVER (PARTITION BY Machine_ID, User_ID, ORDER BY User_Role DESC) AS seqnum
      FROM ex_rt
     ) sub
WHERE seqnum = 1;

Answer 1

在大多数数据库中，您可以使用row_number()：

select t.*
from (select t.*,
             row_number() over (partition by machine_name, user_ID order by user_role desc) as seqnum
      from t
     ) t
where seqnum = 1;

SQL Filter否则会根据列重复条目

1 个答案: