SQL-제약조건

CREATE TABLE SUBJECT(
SUBNO NUMBER(5)
CONSTRAINT SUBJECT_SUBNO_PK PRIMARY KEY,
SUBNAME VARCHAR2(20)
CONSTRAINT SUBJECT_SUBNAME_NN NOT NULL,
TERM VARCHAR2(1)
CONSTRAINT SUBJECT_TERM_CK
CHECK(TERM IN (1, 2)),
TYPE VARCHAR2(4)
CONSTRAINT SUBJECT_TYPE_CK
CHECK(TYPE IN ('필수', '선택')));

CREATE TABLE SUGANG
(STUDNO NUMBER(5) CONSTRAINT SUGANG_STUDNO_FK REFERENCES STUDENT(STUDNO),
SUBNO NUMBER(5) CONSTRAINT SUGANG_SUBNO_FK REFERENCES SUBJECT(SUBNO),
REGDATE DATE,
RESUT NUMBER(3),
CONSTRAINT SUGANG_RESULT_PK PRIMARY KEY(STUDNO, SUBNO));

PRIMARY KEY(STUDNO, SUBNO)