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Question
Formatted question description: https://leetcode.ca/all/176.html
Table: Employee
+-------------+------+ | Column Name | Type | +-------------+------+ | id | int | | salary | int | +-------------+------+ id is the primary key column for this table. Each row of this table contains information about the salary of an employee.
Write an SQL query to report the second highest salary from the Employee
table. If there is no second highest salary, the query should report null
.
The query result format is in the following example.
Example 1:
Input: Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ Output: +---------------------+ | SecondHighestSalary | +---------------------+ | 200 | +---------------------+
Example 2:
Input: Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | +----+--------+ Output: +---------------------+ | SecondHighestSalary | +---------------------+ | null | +---------------------+
Algorithm
Note on null results.
Syntax: IFNULL(expression, alt_value)
Code
SQL
SELECT
IFNULL(
(
SELECT DISTINCT Salary
FROM Employee
ORDER BY Salary DESC
LIMIT 1 OFFSET 1
),
NULL
)
AS SecondHighestSalary
-- below is ok, but not handling null issue
SELECT
(SELECT DISTINCT
Salary
FROM
Employee
ORDER BY Salary DESC
LIMIT 1 OFFSET 1) AS SecondHighestSalary;