MySQL Programming Examples

-- Setup Departments Table & Relationships
CREATE TABLE departments (
    department_id INT PRIMARY KEY,
    dept_name VARCHAR(50)
);

INSERT INTO departments VALUES (1, 'Engineering'), (2, 'Marketing'), (3, 'HR');

-- INNER JOIN: Only matching employees & departments
SELECT e.first_name, d.dept_name 
FROM employees e
INNER JOIN departments d ON e.employee_id = d.department_id;

-- LEFT JOIN: All employees regardless of department match
SELECT e.first_name, d.dept_name 
FROM employees e
LEFT JOIN departments d ON e.employee_id = d.department_id;

+------------+-------------+
| first_name | dept_name   |
+------------+-------------+
| John       | Engineering |
| Alice      | Marketing   |
+------------+-------------+
2 rows in set (0.00 sec)