Second Highest Salary

最新推荐文章于 2020-09-25 01:32:26 发布

原创最新推荐文章于 2020-09-25 01:32:26 发布 · 224 阅读

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本文提供了一种使用SQL从员工表中查询第二高薪资的方法。通过两种不同的查询方式，一种利用子查询和LIMIT关键字，另一种则通过比较最大薪资来实现。即使表中没有数据，查询结果也会返回null。

PROBLEM：

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

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

For example, given the above Employee table, the query should return 200 as the second highest salary. If there is no second highest salary, then the query should return null.

+---------------------+
| SecondHighestSalary |
+---------------------+
| 200                 |
+---------------------+

SOLVE：

# Write your MySQL query statement below
select (
    select distinct Salary 
    from Employee 
    order by Salary Desc 
    limit 1 , 1
)as SecondHighestSalary

# Write your MySQL query statement below
SELECT max(Salary) AS SecondHighestSalary
FROM Employee
WHERE Salary < (SELECT max(Salary) 
                FROM Employee)

分析：即使表中没有数据，最后也会返回null。原理，我也不知道！