Table DEPT (Referenced or Parent Table)

DEPTNO (Primary Key of referenced table)	DNAME	LOC
20	RESEARCH	DALLAS
30	SALES	NEW YORK
40	MARKETING	BOSTON

Table EMP (Dependent or Child Table)

EMPNO	ENAME	JOB	MGR	HIREDATE	SAL	COMM	DEPTNO (Foreign Key; values in dependent table must match a value in unique key or primary key of referenced table)
7329	SMITH	CEO		17-DEC-85	9,000.00		20
7499	ALLEN	VP-SALES	7329	20-FEB-90	7,500.00	100.00	30
7521	WARD	MANAGER	7499	22-FEB-90	5,000.00	200.00	30
7586	JONES	SALESMAN	7521	02-APR-90	2,975.00	400.00	20

INSERT INTO

7571	FORD	MANAGER	7499	23-FEB-90	5,000.00	200.00	50	This row violates the referential constraint because "50" is not present in the referenced table's primary key; therefore, the row is now allowed in the table.
7571	FORD	MANAGER	7499	23-FEB-90	5,000.00	200.00		This row is allowed in the table because a null value is entered in the DEPTNO column; however, if a not null constraint is also defined for this column, this row is not allowed.