문제
Table: Employees
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| employee_id | int |
| name | varchar |
+-------------+---------+employee_id is the column with unique values for this table.
Each row of this table indicates the name of the employee whose ID is employee_id.
Table: Salaries
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| employee_id | int |
| salary | int |
+-------------+---------+
employee_id is the column with unique values for this table.
Each row of this table indicates the salary of the employee whose ID is employee_id.
Write a solution to report the IDs of all the employees with missing information. The information of an employee is missing if:
The employee's name is missing, or
The employee's salary is missing.
Return the result table ordered by employee_id in ascending order.
https://leetcode.com/problems/employees-with-missing-information/description/
예시
Input:
Employees table:
+-------------+----------+
| employee_id | name |
+-------------+----------+
| 2 | Crew |
| 4 | Haven |
| 5 | Kristian |
+-------------+----------+
Salaries table:
+-------------+--------+
| employee_id | salary |
+-------------+--------+
| 5 | 76071 |
| 1 | 22517 |
| 4 | 63539 |
+-------------+--------+
Output:
+-------------+
| employee_id |
+-------------+
| 1 |
| 2 |
+-------------+
Explanation:
Employees 1, 2, 4, and 5 are working at this company.
The name of employee 1 is missing.
The salary of employee 2 is missing.
문제 풀이
SELECT
e.employee_id
FROM
employees AS e
LEFT JOIN
salaries AS s USING(employee_id)
WHERE
s.salary IS NULL
UNION
SELECT
s.employee_id
FROM
salaries AS s
LEFT JOIN
employees AS e USING(employee_id)
WHERE
e.name IS NULL
ORDER BY 1;SQL을 독학하시는 분들에게 도움이 되길 바라며,
혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.
