SQL>
SQL>
SQL> create table subjects (
2 subject_id number not null,
3 subject_name varchar2(30) not null,
4 description varchar2(4000)
5 )
6 tablespace users;
Table created.
SQL>
SQL> alter table subjects add constraint pk_subjects primary key (subject_id);
Table altered.
SQL>
SQL> create table courses (
2 course_id number not null,
3 course_name varchar2(60) not null,
4 subject_id number not null,
5 duration number(2),
6 skill_lvl varchar2(12) not null
7 )
8 tablespace users;
Table created.
SQL>
SQL> alter table courses add constraint pk_courses primary key (course_id);
Table altered.
SQL>
SQL> alter table courses add constraint fk_course_subj foreign key (subject_id) references subjects (subject_id);
Table altered.
SQL>
SQL> alter table courses add constraint ck_level check(
2 skill_lvl in ('BEGINNER', 'INTERMEDIATE', 'ADVANCED')
3 );
Table altered.
SQL>
SQL> drop table subjects cascade constraints;
Table dropped.
SQL> drop table courses cascade constraints;
Table dropped.
SQL>