Relational Model’da Constraints

CREATE TABLE Enrolled ( sid CHAR(20), cid CHAR(20), grade CHAR(10), PRIMARY KEY (sid, cid), FOREIGN KEY (sid) REFERENCES Students ON DELETE CASCADE ON UPDATE NO ACTION )
Cascade, silme durumunda bütün kayıtları siler

CREATE TABLE Enrolled ( sid CHAR(20), cid CHAR(20), grade CHAR(10), PRIMARY KEY (sid, cid), FOREIGN KEY (sid) REFERENCES Students ON DELETE CASCADE ON UPDATE NO ACTION )