数据表
Employee 表: +-------------+------+ | Column Name | Type | +-------------+------+ | id | int | | salary | int | +-------------+------+ id 是这个表的主键。 表的每一行包含员工的工资信息。
题目2:第二高的薪水
编写一个 SQL 查询,获取并返回 Employee 表中第二高的薪水 。如果不存在第二高的薪水,查询应该返回 null 。
查询结果如下例所示。
示例 1: 输入: Employee 表: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ 输出: +---------------------+ | SecondHighestSalary | +---------------------+ | 200 | +---------------------+ 示例 2: 输入: Employee 表: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | +----+--------+ 输出: +---------------------+ | SecondHighestSalary | +---------------------+ | null | +---------------------+
解答
select ifNull( (select distinct salary from Employee order by Salary Desc limit 1,1),null ) as SecondHighestSalary;
题目3:第N高的薪水
编写一个SQL查询来报告 Employee 表中第 n 高的工资。如果没有第 n 个最高工资,查询应该报告为 null 。
查询结果格式如下所示。 示例 1: 输入: Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ n = 2 输出: +------------------------+ | getNthHighestSalary(2) | +------------------------+ | 200 | +------------------------+ 示例 2: 输入: Employee 表: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | +----+--------+ n = 2 输出: +------------------------+ | getNthHighestSalary(2) | +------------------------+ | null | +------------------------+
解答
CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT BEGIN declare m int; SET m = N-1; RETURN ( # Write your MySQL query statement below. select ifNull( ( select distinct salary from Employee order by salary desc limit 1 offset m ),null) ); END