SELECT country_id, country_name FROM countries WHERE country_id IN ('US', 'UK', 'CN');
SELECT country_id, street_address, city FROM locations WHERE country_id IN ('US', 'UK', 'CN');
SELECT c.country_name, c.country_id, l.country_id, l.street_address, l.city FROM countries c LEFT JOIN locations l ON l.country_id = c.country_id WHERE c.country_id IN ('US', 'UK', 'CN')
SELECT country_name FROM countries c LEFT JOIN locations l ON l.country_id = c.country_id WHERE l.location_id IS NULL ORDER BY country_name;
SELECT r.region_name, c.country_name, l.street_address, l.city FROM regions r LEFT JOIN countries c ON c.region_id = r.region_id LEFT JOIN locations l ON l.country_id = c.country_id WHERE c.country_id IN ('US', 'UK', 'CN');
SELECT * FROM countries;
SELECT * FROM departments;
SELECT * FROM dependents;
SELECT * FROM employees;
SELECT * FROM jobs;
SELECT * FROM locations;
SELECT * FROM regions;
