Join 문

1. INNER JOIN:
   INNER JOIN은 두 테이블 간에 일치하는 행만 검색합니다

SELECT employees.first_name, employees.last_name, departments.department_name
FROM employees
INNER JOIN departments ON employees.department_id = departments.department_id;

2. LEFT JOIN (또는 LEFT OUTER JOIN):
   LEFT JOIN은 왼쪽 테이블의 모든 행과 오른쪽 테이블의 일치하는 행을 검색합니다.

SELECT departments.department_name, employees.first_name, employees.last_name
FROM departments
LEFT JOIN employees ON departments.department_id = employees.department_id;

3. RIGHT JOIN (또는 RIGHT OUTER JOIN):
   RIGHT JOIN은 LEFT JOIN의 반대입니다. 오른쪽 테이블의 모든 행과 왼쪽 테이블의 일치하는 행을 검색합니다.

SELECT employees.first_name, employees.last_name, departments.department_name
FROM employees
FULL OUTER JOIN departments ON employees.department_id = departments.department_id;