SQL Taskbook Level 2.3
Given a table:
| id | first_name | last_name | salary | department | manager_id | start_work_date |
| 1 | Aaron | Gold | 4300.00 | PHP | 1 | 2012-02-10 |
| 2 | Marina | Page | 4000.00 | React | NULL | 2010-12-10 |
| 3 | Max | Tyler | 1500.00 | PHP | 1 | 2020-05-30 |
| 4 | Oliver | Barrera | 1500.00 | Node.js | NULL | 2020-08-31 |
| 5 | Andrew | Green | 900.00 | PHP | 1 | 2023-08-31 |
Solve the following tasks for it:
Задание 1
List the unique departments in which employees work.
Задание 2
Find employees who are paid above the average salary in their department.
Задание 3
Display the first and last names of employees who have worked for more than 5 years.
Задание 4
Find employees who do not have a manager set (NULL in the manager_id field).
Задание 5
Display a list of employees sorted by hire date in descending order.