EER Relational Mapping

How to map EER TO RELATIONSHIP

ET

THE ABOVE IS NOT GOOD,the bottom one is good however, it is impossible in relationship model because of atomic, we will lose attribute c in relation model

ET-A-F

F is multiple value, so there are tow table

ET1-A-ET2

foreign key

exmple: ET2 is mandatary to participate r.bottom is bette，这样就不会有null value了

ET1-R-ET2-1-N

ET1-R-ET2-N-M

ET1-R-A-ET2

Case 1

Case 2

Case 3

Case 4

ET-B-ET1-ET2

Summary