SQL实现LeetCode(177.第N高薪水)

[LeetCode] 177.Nth Highest Salary 第N高薪水

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

+----+--------+
| 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.

这道题是之前那道Second Highest Salary的拓展，根据之前那道题的做法，我们可以很容易的将其推展为N，根据对Second Highest Salary中解法一的分析，我们只需要将OFFSET后面的1改为N-1就行了，但是这样MySQL会报错，估计不支持运算，那么我们可以在前面加一个SET N = N - 1，将N先变成N-1再做也是一样的：

解法一：

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

解法二：

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

解法三：

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

Second Highest Salary

参考资料：

https://leetcode.com/discuss/88875/simple-answer-with-limit-and-offset

https://leetcode.com/discuss/63183/fastest-solution-without-using-order-declaring-variables

[LeetCode] 177.Nth Highest Salary 第N高薪水

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