Data models in dbms defomes how data is arranged,stored, accessed and updated in database management system.Data models in dbms defines the logical structure of database and it gives the logical view to the users that how data is organized in dbms.It also describes the logical structure,semantics,and integrity constraints applied on data.

Hierarchical model

Network model

Relarional model

Hierarchical model

Hierarchical model organizes data in hierarchy im inverted tree structure in which each data is called as node or segement.Topmost node is called root.Nodes at lower level is called childs and nodes at higher level is called as parents.This relationship is called pareent-child relationship.

In hierarchical database model each parent has many childs but child has only one parent.Hierarchical model provides one to one relationship and one to many relationship betweens its nodes.

Network model

Network data model is a extension of hierarchical model whcih organizes data in graph data structure where childs has more than one parents and parents also has many childs.Network data model represents data in parent-child relationship in more complex way than hierarchical model and overcomes its limitations.

Network model provides one to one,one to many,many to one and many to many relationships between data nodes (parents and childs).

Relational model

and alsodefines the realtion between them.Relational model is based on the mathematical concept of “relation”.The database based on relational model is called as relational database.Here are some key terms of relational model.

Relation

A table is called as relation in relation model which has columns and rows.

Attributes

Attributes a are the properties ot column headers of a relationa in relational model.

Domain values

Domain values are the all the possible sets of values of columns in a trlation.

Tuple

A row om a relation is called as tuple.

Degree of relation

Degree of a relation is the total numbers of attributes in a relation.

Cardinality of relation

Cardinality of a relation is total numbers of tuples (rows) in a relation.