USING절, NATURAL JOIN 쿼리 결과 특징

INNER JOIN 한 결과 ( USING 이나 NATURAL JOIN을 사용하지 않은 이너 조인의 결과)

• 양쪽 테이블에 있는 DEPTNO가 출력

SELECT *
FROM EMP A
INNER JOIN DEPT B
ON A.DEPTNO = B.DEPTNO;

 

USING / NATURAL JOIN 한 결과

• DEPTNO가 1개만 출력
• JOIN 기준인 컬럼이 맨 앞에 출력

SELECT *
FROM EMP A
JOIN DEPT B
USING (DEPTNO);

SELECT *
FROM EMP A
NATURAL JOIN DEPT B;