Question

数据：

 Id | Salary |
---------------
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |

我正在尝试使用以下代码获得Nth最高薪水。例如，如果我通过＆＃34; N＆＃34;值为1，下面的代码给我100，而它应该是300.我不知道为什么＆＃34;顺序由desc＆＃34;工作不正常。

CREATE FUNCTION gethighestsalary(N INT) RETURNS INT
BEGIN
DECLARE rank INT;
SET @rank = 0;
RETURN (
select a.salary FROM (select salary, @rank:=@rank+1 as chk from Employee group by salary order by salary desc) AS a
where a.chk= N
);
END

Answer 1

删除group by

select a.salary, a.chk
FROM 
(  
    select salary, @rank := @rank + 1 as chk 
    from t 
    cross join (select @rank := 0) r
    order by salary desc
) AS a
where a.chk = 1

SQLFiddle demo

否则order by将无效，因为它在分组后排序，然后您的行号错误。

或者保持分组并将其放入另一个子查询中并在之后排名。

Answer 2

以下代码对您有所帮助，

SELECT Salary FROM Employee Emp1 
WHERE (N-1) = ( 
                SELECT COUNT(DISTINCT(Emp2.Salary)) 
                FROM  Employee Emp2
                WHERE Emp2.Salary > Emp1.Salary
              )

SQL Fiddle Demo

Mysql中的行号函数，面临Order by子句的问题

2 个答案:

SQLFiddle demo