The record based database model consists of a number of fixed format records of different types.
Each record type defines a fixed number of fields of a fixed length.
Are of three types:
i. Relational
ii. Network
iii. Hierarchical
Hierarchical Data Model
It organizes data into a tree data structure such that each record has one owner.
Advantages of Hierarchical data model
It is the easiest model of database.
Secure since a child cannot be updated without consulting the parent in the tree structure.
If parent is known, searching is easy and fast.
Efficient in handling one to many relationships.
Disadvantages of Hierarchical data model
It is old fashioned, outdated database model.
Modification and addition of child is not possible without consulting parent hence it is a non-flexible data model.
Cannot handle many to many relationship.
Increases redundancy since same data has to be written in different places.
Network Data Model
Data is represented as a collection of records and relationships are represented by sets.
Takes the form of a tree like structure and uses a many to many relationship approach.
Nodes are allowed to have multiple parent nodes.
Relational Data Model
Uses a collection of tables to represent both data and relationships among those data.
Parts of a Relation
Relation Heading
Is a set of (attribute, domain) pairs i.e (column, column-type) pairs.
Relation body
Is a set of tuples (i.e rows).
Advantages of Relational Data Model
Handles many to many relationships.
Reduces redundancy since data can be referenced instead of being duplicated.
Constraints on data can be easily enforced.
