Join operations -Example Relation course course id title dept name credits BIO-301 Genetics Biology 4 CS-190 Game Design Comp.Sci. 4 CS-315 Robotics Comp.Sci. 3 Relation prereg course id prereg id BIO-301 BIO-101 CS-190 CS-101 CS-347 CS-101 Observe that prereq information is missing for CS-315 and course information is missing for CS-437 Database System Concepts-6th Edition 4.4 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 6 4.4 ©Silberschatz, Korth and Sudarshan th Edition Join operations – Example Relation course Relation prereq Observe that prereq information is missing for CS-315 and course information is missing for CS-437