Forth, Each row in table DEPT must include a unique DEPT# value; likewise, each row in table EMP must include a unique EMP# value. The columns DEP# and EMP# are the primary keys.
Fifth, Each DEPT# value in table EMP must exist as a DEPT# value in table DEPT, to reflect the fact that every employee must be assigned to an existing department. Column DEPT# in table EMP is a foreign key, referencing the primary key of table DEPT.