Question

Number | UserId | Priority
--------------------------
1234   | User1  | 1
2345   | User1  | 2
5678   | User1  | 3
2456   | User2  | 1
6556   | User2  | 2
2435   | User3  | 1
6567   | User3  | 2

我想根据Priority

的最高值提取下面的行列表

Number | UserId | Priority
--------------------------
5678   | User1  | 3
6556   | User2  | 2
6567   | User3  | 2

将表名称视为用户代码，可以为此人提供sql查询帮助。

Answer 1

Select A.number,A.userId,A.Priority from TableName A 
inner join
(
 Select UserId,Max(Priority) as Priority from  TableName group by UserId
) B on A.Priority =B.Priority  and A.UserId=B.UserId

Sql Fiddle Demo

Answer 2

另一种写作方式是

select
a.*
from
TableName a
left join TableName b
on a.Priority < b.Priority 
and a.UserId = b.UserId
where b.Priority is null

LEFT JOIN的工作原理是，当a.priority处于最大值时，没有b.priority具有更大的值，b行值将为NULL。

看到它在sqlfiddle中正常工作。

Answer 3

SELECT A.Number, A.UserId, A.Priority 
FROM usercodeTBL A 
INNER JOIN(SELECT UserId, Max(Priority) AS Priority FROM usercodeTBL GROUP BY UserId) B 
ON A.Priority = B.Priority  AND A.UserId = B.UserId
ORDER BY UserId, Priority DESC

SQL查询以下操作

3 个答案: