SQL practice: A Table Joined to Itself

List every employee with their manager's name, showing NULL where there is none.

List every employee with their manager's name and their manager's salary.

Find the employees who earn more than their own manager.

List only the employees who have a manager. (Which join should you use now?)

List the employees who have no manager.

Show every stock transfer with the from-branch and to-branch names.

Show every stock transfer with the from-branch city and to-branch city.

Show each employee, their manager's name, and their manager's branch name. (Three aliases now.)

Explain why SELECT employees.employee_name FROM employees e JOIN employees m ... would fail.

List each pair of employees who work in the same branch, once per pair, with the lower employee_id first. Every pair shows up twice. Fix it.