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 |
+---------------------+
此题的难点是：
- 针对可能存在的重复数值，选出唯一的数值(使用
distinct)； - 选取第二个数值，则需要使用
limit,offset确定数值； - 查询的数值可能为不存在，此时就需要返回
NULL(使用IFNULL).
答题如下所示：
# Write your MySQL query statement below
select
ifnull(
(select distinct Salary from Employee order by Salary desc limit 1,1),
NULL
)
as SecondHighestSalary
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