Mapping constraints in a database define rules that entities and their relationships must adhere to.
Two main types of mapping constraints are mapping cardinalities and participation constraints.
1. Mapping Cardinalities:
Mapping cardinalities specify how many entities of one type can be associated with entities of another type through a relationship set. For binary relationship sets (involving two entity sets), the mapping cardinality can be categorized as:
a. One to One (1:1): An entity in set A is associated with at most one entity in set B, and vice versa.
b. One to Many (1:N): An entity in set A can be associated with any number of entities in set B, but an entity in set B can be associated with at most one entity in set A.
c. Many to One (N:1): An entity in set A can be associated with at most one entity in set B, while an entity in set B can be associated with any number of entities in set A.
d. Many to Many (N:N): An entity in set A can be associated with any number of entities in set B, and vice versa.
2.Participation Constraints: Participation constraints describe the involvement of entity sets in a relationship. There are two types of participation:
1.Partial Participation: Not all entities in an entity set are required to participate in the relationship.
ii. Total Participation: Every entity in an entity set must participate in the relationship.