create_table.txt

CREATE TABLE STUDENT
(	s_id VARCHAR(20) not null,
	s_pwd VARCHAR(20) not null,
	s_name VARCHAR(20) not null,
	s_grade NUMBER not null,
	s_major VARCHAR(50) not null,
	CONSTRAINT student_pk PRIMARY KEY (s_id)
);

CREATE TABLE course(
	c_id VARCHAR(20),
	c_name VARCHAR(100),
	c_id_no NUMBER,
	c_time_start VARCHAR(20),
	c_time_end VARCHAR(20),
	c_day NUMBER,
	c_unit NUMBER,
	c_max NUMBER,
	c_where VARCHAR(50),
	CONSTRAINT c_pk PRIMARY KEY (c_id, c_id_no)
);

CREATE TABLE enroll(
	s_id VARCHAR(20),
   	c_id VARCHAR(20),
	c_id_no NUMBER,
    	e_year NUMBER,
    	e_semester NUMBER,
    	CONSTRAINT e_pk PRIMARY KEY (s_id, c_id, c_id_no) ,
	CONSTRAINT e_s_fk FOREIGN KEY(s_id)
	REFERENCES student (s_id),
   	CONSTRAINT e_c_fk FOREIGN KEY (c_id, c_id_no)
   	REFERENCES  course (c_id, c_id_no)
);

CREATE TABLE teach
(
    p_id VARCHAR(20),
    c_id VARCHAR(20),
    c_id_no NUMBER,
    t_year NUMBER,
    t_semester NUMBER,
    CONSTRAINT t_pk PRIMARY KEY (p_id, c_id, c_id_no, t_year, t_semester),
    CONSTRAINT t_p_fk FOREIGN KEY (p_id)
    REFERENCES professor (p_id),
    CONSTRAINT t_c_fk FOREIGN KEY (c_id, c_id_no) 
    REFERENCES  course (c_id, c_id_no)
 );

CREATE TABLE professor
(
    p_id	VARCHAR(20) not null,
    p_pwd    VARCHAR(20)   not null,
    p_name  VARCHAR(20)   not null,
    p_major  VARCHAR(50)   not null,
    CONSTRAINT p_pk PRIMARY KEY (p_id)
);