Mapping Constraints are sub divided into two parts that is Cardinality Ratio and Participation Constraints
Cardinality Ratio: It express the number of entities to which another entity can be associated via a relationship.
One to One: An entity of entity-set A can be associated with at most one entity of entity-set B and an entity in entity-set B can be associated with at most one entity of entity-set A.
One to Many: An entity of entity-set A can be associated with any number of entities of entity-set B and an entity in entity-set B can be associated with at most one entity of entity-set A.
Many to One: An entity of entity-set A can be associated with at most one entity of entity-set B and an entity in entity-set B can be associated with any number of entities of entity-set A.
Many to Many: An entity of entity-set A can be associated with any number of entities of entity-set B and an entity in entity-set B can be associated with any number of entities of entity-set A.
Participation Constraints:-
Total Participation-Shown with double lines.In this figure,employ is having total participation in department.
Partial Participation-Shown with single line.In this figure,department is having partial participation with employ.
NOTE-Weak entity always have total participation with the other entity as it is not having primary key which uniquely identifies its tuple.
Cardinality Ratio: It express the number of entities to which another entity can be associated via a relationship.
One to One: An entity of entity-set A can be associated with at most one entity of entity-set B and an entity in entity-set B can be associated with at most one entity of entity-set A.
One to Many: An entity of entity-set A can be associated with any number of entities of entity-set B and an entity in entity-set B can be associated with at most one entity of entity-set A.
Many to One: An entity of entity-set A can be associated with at most one entity of entity-set B and an entity in entity-set B can be associated with any number of entities of entity-set A.
Many to Many: An entity of entity-set A can be associated with any number of entities of entity-set B and an entity in entity-set B can be associated with any number of entities of entity-set A.
Participation Constraints:-
Total Participation-Shown with double lines.In this figure,employ is having total participation in department.
Partial Participation-Shown with single line.In this figure,department is having partial participation with employ.
NOTE-Weak entity always have total participation with the other entity as it is not having primary key which uniquely identifies its tuple.