Need help with tables beginner........

Question

can some one help me straightned out these errors, am trying to teach myself some sql for and am using my buddies school books. this is the problem.
Create the following relations in SQLPLUS. The columns involved in composing the primary key for each table are marked with a *.
* FACULTY (*fss_num varchar2(20), name varchar2(20), address varchar2(20), age number,salary number(10,2))
* ATTENDS (*sss_num varchar2(20), *c_num number, sec_num number)
* SECTION (*c_num number,*sec_num number,fss_num varchar2(20))
* STUDENT (*sss_num varchar2(20), name varchar2(20), address varchar2(20), age number)
* COURSE (*c_num number, cdesc varchar2(20), credits number, size_limit number)
My solution: seems right am following another example but i get various errors.
DROP TABLE ATTENDS;
DROP TABLE STUDENT;
DROP TABLE SECTION;
DROP TABLE COURSE;
DROP TABLE FACULTY;
CREATE TABLE FACULTY
     (FSS_NUM      VARCHAR2(20) NOT NULL,
     NAME          VARCHAR2(20) NOT NULL,
     ADDRESS      VARCHAR2(20),
     AGE           NUMBER,
     SALARY           NUMBER(10,2),
     CONSTRAINT FACULTY_PK PRIMARY KEY (FSS_NUM));
CREATE TABLE COURSE
     (C_NUM           NUMBER NOT NULL,
     CDESC           VARCHAR2(20),
     CREDITS      NUMBER,
     SIZE_LIMIT      NUMBER,
     CONSTRAINT COURSE_PK PRIMARY KEY (C_NUM));
CREATE TABLE STUDENT
     (SSS_NUM      VARCHAR2(20) NOT NULL,
     NAME           VARCHAR2(20) NOT NULL,
     ADDRESS      VARCHAR2(20),
     AGE           NUMBER,
     CONSTRAINT STUDENT_PK PRIMARY KEY (SSS_NUM));
CREATE TABLE ATTENDS
     (SSS_NUM      VARCHAR2(20) NOT NULL,
     C_NUM           NUMBER NOT NULL,
     SEC_NUM      NUMBER NOT NULL,
     CONSTRAINT ATTENDS_PK PRIMARY KEY (SSS_NUM, C_NUM),
     CONSTRAINT ATTENDS_FK1 FOREIGN KEY (SSS_NUM) REFERENCES STUDENT(SSS_NUM),
     CONSTRAINT ATTENDS_FK2 FOREIGN KEY (C_NUM) REFERENCES COURSE(C_NUM));
CREATE TABLE SECTION
     (C_NUM           NUMBER NOT NULL,
     SEC_NUM      NUMBER NOT NULL,
     FSS_NUM      VARCHAR2(20) NOT NULL,
     CONSTRAINT SECTION_PK PRIMARY KEY (C_NUM, SEC_NUM),
     CONSTRAINT SECTION_FK1 FOREIGN KEY (C_NUM) REFERENCES COURSE(C_NUM));

Answer 1

Hi,
If you want to give Primary Key constraint for a column, no need to create NOT NULL constraint again for the same column.
If you create Primary Key constraint for a composite column, only possible to create Foreign Key on the same composite column.
Mistake.....if PRIMARY KEY(SSS_NUM, C_NUM), we should not either FOREIGN KEY(SSS_NUM) or FOREIGN KEY(C_NUM). We should create only like FOREIGN KEY(SSS_NUM, C_NUM).
Regards,
Sailaja