Violating Constraint

UPDATE employees
SET       department_id = 55
WHERE  department_id = 110;

UPDATE employees
            *
ERROR at line 1:

ORA-02291: integrity constraint (HR.EMP_DEPT_FK)
violated - parent key not found

Department 55 doesn't exist in the parent table.



You cannot delete a row that contains a primary key that is used as a foreign key in another table.

DELETE FROM departments
WHERE            department_id = 60;

DELETE FROM department
                     *
ERROR at line 1:

ORA-02292: integrity constraint (HR.EMP_DEPT_FK)
violated - child record found

The department number 60 is being used as a foreign key in the child table.