[LeetCode] Nth Highest Salary 第N高薪水 LeetCode All in One 題目講解彙總(持續更新中...)

時間 2019-12-08

標籤 leetcode nth highest salary 薪水題目講解彙總持續更新简体版

原文原文鏈接

Write a SQL query to get the nth highest salary from the Employee table.html

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

For example, given the above Employee table, the nth highest salary where n = 2 is 200. If there is no nth highest salary, then the query should return null.post

這道題是以前那道Second Highest Salary的拓展，根據以前那道題的作法，咱們能夠很容易的將其推展爲N，根據對Second Highest Salary中解法一的分析，咱們只須要將OFFSET後面的1改成N-1就好了，可是這樣MySQL會報錯，估計不支持運算，那麼咱們能夠在前面加一個SET N = N - 1，將N先變成N-1再作也是同樣的：url

解法一：spa

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  SET N = N - 1;
  RETURN (
      SELECT DISTINCT Salary FROM Employee GROUP BY Salary
      ORDER BY Salary DESC LIMIT 1 OFFSET N
  );
END

根據對Second Highest Salary中解法四的分析，咱們只須要將其1改成N-1便可，這裏卻支持N-1的計算，參見代碼以下：code

解法二：htm

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  RETURN (
      SELECT MAX(Salary) FROM Employee E1
      WHERE N - 1 =
      (SELECT COUNT(DISTINCT(E2.Salary)) FROM Employee E2
      WHERE E2.Salary > E1.Salary)
  );
END

固然咱們也能夠經過將最後的>改成>=，這樣咱們就能夠將N-1換成N了：blog

解法三：leetcode

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  RETURN (
      SELECT MAX(Salary) FROM Employee E1
      WHERE N =
      (SELECT COUNT(DISTINCT(E2.Salary)) FROM Employee E2
      WHERE E2.Salary >= E1.Salary)
  );
END