that4loopgirl

There are two types of constraints:  Mapping cardinalities,  Participation constraints 1. Mapping cardinalities Mapping cardinalities, also known as cardinality ratio, expresses the number of entities to which another entities can be associated via relationship set. The mapping cardinality must be one of the following types for describing a binary relationship set R between entity set A and B :  One to one : An entity in A is associated with at most one entity in B , and entity in B is associated with at most one entity in A .  One to many : An entity in A is associated with zero or more number of entities in B . While an entity in B can be associated with at most one entity in A .  Many to one : An entity in A is associated with at most one entity in B . While an entity in B , can be associated with zero or more number of entities in A .  Many to many : An entity in A is associated with zero or more number of entities in B , and an entity in B is associa