leetcode 176. Second Highest Salary

176. Second Highest Salary

 

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Total Accepted: 21825
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Difficulty: Easy

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 second highest salary is 

200

.
If there is no second highest salary, then the query should return 

null

.

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

注意 order by  后面的Desc表示降序排列，asc表示升序排列

as

as不是给表里的字段取别名，而是给查询的结果字段取别名。其目的是让查询的结果展现更符合人们观看习惯,在多张表查询的时候可以直接的区别多张表的同名的字段。
比如：
1、selec name as “姓名” ,sex as "性别" from user
2、select u.name as “姓名”,o.name as "英文名" ,u.sex as "性别" from user u ,other o where u.id = o.id;