Question

我想写一个SQL查询来从Employee表中获得第n个最高薪水。

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

我尝试了什么？

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  RETURN (
      # Write your MySQL query statement below.
      SELECT Salary
        FROM Employee
        ORDER BY Salary desc
        Limit N,1
  );
END

问题：我希望返回行N-1而不是N，因为行从0开始。我试图设置一个变量，但它不起作用，

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
SET M=N-1;
  RETURN (
      # Write your MySQL query statement below.
      SELECT Salary
        FROM Employee
        ORDER BY Salary desc
        Limit M,1
  );
END

Answer 1

你可以减少变量：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  set n = n - 1;
  RETURN (
      # Write your MySQL query statement below.
      SELECT Salary
        FROM Employee
        ORDER BY Salary desc
        Limit n, 1
  );
END;

如果必须使用单独的var，请先声明它：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  declare m int;
  set m = n - 1;
  RETURN (
      # Write your MySQL query statement below.
      SELECT Salary
        FROM Employee
        ORDER BY Salary desc
        Limit m, 1
  );
END;

Demo

Answer 2

从员工e1中选择DISTINCT薪水，其中2 =（从员工e2中选择计数（DISTINCT薪水），其中e1.salary＆lt; = e2.salary）;

其中2 =数字。您可以从员工表中找到任何最高薪水。比如3rd，然后用3替换2。

Answer 3

这还将考虑存在空值或2个相同最高薪水的情况

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
declare m int;
set m = n-1;
  RETURN (SELECT DISTINCT Salary AS getNthHighestSalary
      FROM Employee
      ORDER BY Salary DESC
      LIMIT m, 1

  );
END

获得第n个最高薪水

3 个答案:

Demo