Foreign Key

SQL> CREATE TABLE departments
  2  (department_id             number(10)            not null,
  3   department_name           varchar2(50)      not null,
  4   CONSTRAINT departments_pk PRIMARY KEY (department_id)
  5  );

Table created.

SQL>
SQL>
SQL> CREATE TABLE employees
  2  ( employee_id          number(10)      not null,
  3    last_name            varchar2(50)      not null,
  4    job_id               varchar2(30),
  5    department_id        number(10),
  6    salary               number(6),
  7    manager_id           number(6),
  8    CONSTRAINT           employees_pk PRIMARY KEY (employee_id),
  9    CONSTRAINT           fk_departments FOREIGN KEY (department_id)
 10                         REFERENCES departments(department_id)
 11  );

Table created.

SQL>