- NOT NULL
- UNIQUE：CONSTRAINT uc_PersonID UNIQUE (Id_P,LastName)
- PRIMARY KEY：CONSTRAINT pk_PersonID PRIMARY KEY (Id_P)
- FOREIGN KEY：FOREIGN KEY (Id_P) REFERENCES Persons(Id_P)
- CHECK：CONSTRAINT chk_Person CHECK (Id_P>0 AND City='Sandnes')
- DEFAULT：City varchar(255) DEFAULT 'Sandnes'
ON DELETE CASCADE→关系表的级联删除
