What is Mapping Constraints in Database Management System ?

Define it in brief. 

Last updated:4/3/2019 1:11:11 AM

1 Answers

Rahul Roi
Rahul Roi

Mapping Constraints in DBMS

What is Mapping Constraints in Database Management System ?

The mapping constraint is the data constraint that expresses the number of entities to which another entity can be related via a relationship set.

These are most useful in describing the relationship sets that involve more than two entity sets.

For binary relationship set R on an entity set X and Y, there are four possible mapping cardinalities. These are as follows:

  • One to one (1:1)
  • One to many (1: M)
  • Many to one (M:1)
  • Many to many (M: M)

In one-to-one mapping (1:1):- That is an entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with at most one entity of entity-set X.

What is Mapping Constraints in Database Management System ?

For Example - Whether Employee and Department are 2 entity sets, then we can define a one to one relationship ‘Manages’ between an Employee entity and a Department entity i.e. one employee manages at most one department and one department is managed by at most one employee.

What is Mapping Constraints in Database Management System ?

One to many (1: M):- When An entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

What is Mapping Constraints in Database Management System ?

Many to one (M:1): When An entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

What is Mapping Constraints in Database Management System ?

Many to Many (M: M):- When An entity of entity-set X can be associated with any number of entities of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

What is Mapping Constraints in Database Management System ?

AND

These relations are used in DataBaseManagement System.


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