leetcode - database - 177. Nth Highest Salary （Oracle）

题目链接：https://leetcode.com/problems/nth-highest-salary/description/

题意：查询出表中工资第N高的值

思路：

1、先按照工资从高到低排序（注意去重）

select distinct Salary from Employee order by Salary desc

　　

2、使用rownum给查询出的数据标注行号

select rownum ro, s.Salary from (select distinct Salary from Employee order by Salary desc)s

　　

3、查询行号>=N并且<=N（即N位）的值，注意在oracle函数中 修改查询出的字段名要用into

CREATE FUNCTION getNthHighestSalary(N IN NUMBER) RETURN NUMBER IS
result NUMBER;
BEGIN
    /* Write your PL/SQL query statement below */
    select Salary into result from (select rownum ro, s.Salary from (select distinct Salary from Employee order by Salary desc)s) where ro>=N and ro<=N;
    RETURN result;
END;