What is mapping constraints and types or explains[DBMS-3]

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Mapping constraints 

-A mapping constraints is data constraints that express the number of entity to which another entity can be related via a relationship sets. 
-It is most useful in describing relationship sets that involve more than two entity sets.  
-There are four types of mapping constraints.
-one to one 
-one to many
-many to one 
-many to many

one to one:

Let us consider two entity sets A and B. An entity in A is associated with at most one entity in B.An entity in B is associated with at most one entity in A.












one to many:

Let us consider two entity sets A and B. An entity in A is associated with any number (0 or more) of the entity in B and An entity in B is associated with at most one entity in A.












many to one :

let us consider two entity sets A and B. An entity in A is associated with at most one entity in B and an entity in B is associated with any number of the entity in A












many to many :

Let us consider two entity sets A and B. An entity in A is associated with any number of the entity in B and an entity in B is associated with any number of the entity in A.









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