SQL 10-4. FOREIGN KEY REFERENCES 제약 조건

CREATE TABLE 고객 (
            고객아이디 VARCHAR(20) NOT NULL,
            고객이름 VARCHAR(10) NOT NULL,
            나이 INT,
            등급 VARCHAR(10) NOT NULL,
            직업 VARCHAR(20),
            적립금 INT DEFAULT 0,
            PRIMARY KEY(고객아이디) 
);

CREATE TABLE 제품 (
            제품번호 CHAR(3) NOT NULL,
            제품명 VARCHAR(20),
            재고량 INT,
            단가 INT,
            제조업체 VARCHAR(20),
            PRIMARY KEY(제품번호),
            CHECK (재고량 〉= 0 AND 재고량 〈=10)
);

CREATE TABLE 주문 (
            주문번호 CHAR(3) NOT NULL,
            주문고객 VARCHAR(20),
            주문제품 CHAR(3),
            수량 INT,
            배송지 VARCHAR(30),
            주문일자 DATETIME,
            PRIMARY KEY(주문번호),
            FOREIGN KEY(주문고객) REFERENCES 고객(고객아이디),
            FOREIGN KEY(주문제품) REFERENCES 제품(제품번호)
);