MySQL Programming Examples

-- UNION: Combines datasets and removes duplicate entries
SELECT first_name, 'Employee' AS role FROM employees
UNION
SELECT dept_name, 'Department' AS role FROM departments;

-- UNION ALL: Retains all rows including duplicates
SELECT first_name FROM employees
UNION ALL
SELECT last_name FROM employees;

+------------+------------+
| first_name | role       |
+------------+------------+
| John       | Employee   |
| Alice      | Employee   |
| Carol      | Employee   |
| Engineering| Department |
| Marketing  | Department |
+------------+------------+