[DB] 7. 테이블 병합(JOIN)

# 테이블 병합(JOIN) 

데이터 베이스 내의 여러 테이블에서 가져온 레코드를 조합하여 하나의 테이블이나 결과 집합으로 표현합니다. 

 

SELECT 컬럼명1, 컬럼명2 ... FROM 테이블명1 (INNER, LEFT, RIGHT) JOIN 테이블명2 ON 테이블명1.필드명 = 테이블명2.필드명

 

● INNER : 교집합

LEFT  : 테이블1을 기준으로 데이터를 병합
RIGHT : 테이블2를 기준으로 데이터를 병합

예)
INSERT INTO tb_order VALUES('0000000001', 1000, '양말', now(), 8);
INSERT INTO tb_order VALUES('0000000002', 2000, '손수건', NOW(), 2);
INSERT INTO tb_order VALUES('0000000003', 3500, '양말2', NOW(), 3);
INSERT INTO tb_order VALUES('0000000004', 7000, '반바지', NOW(), 4);
INSERT INTO tb_order VALUES('0000000005', 2500, '반팔', NOW(), 2);
INSERT INTO tb_order VALUES('0000000006', 9500, '커피', NOW(), 3);
INSERT INTO tb_order VALUES('0000000007', 7300, '컵', NOW(), 4);
INSERT INTO tb_order VALUES('0000000008', 10000, '치마', NOW(), 8);
INSERT INTO tb_order VALUES('0000000009', 11000, '블라우스', now(), 8);
INSERT INTO tb_order VALUES('0000000010', 8000, '바지', now(), 8);

예)
SELECT mem_userid, mem_name, mem_gender, ord_price, ord_product, ord_regdate
FROM tb_member INNER JOIN tb_order ON tb_member.mem_idx = tb_order.ord_memidx