Users, Database systems to address common issues in applications handling large volumes of data which are also data-intensive. The database allows quick and easy management data. At any time, any point you can retrieve from the database added and searched based.
Users, Databases can be differentiated based on functions and model of the data. A data model describes a container for storing data and the process of storing and retrieving data from that containers. The analysis and designs of data models have been the basis of the evolution of databases. Each model has evolved from the previous one. The commonly used Database Models are as follows:-
- Flat File Database Model.
- Hierarchical Data Model.
- Network Data Model
- Relation Data Model
Flat File (DM)
In this, the database consists of only one table or file. This model is used for simple databases – for example, to store the roll numbers, names, subjects, and marks of a group of students. This model cannot handle very complex data. It can cause redundancy when data is repeated more than once.
In this model, different records are inter-related through hierarchical or tree-like structures. In this model, relationships are thought of in terms of children and parents. A parent record can have several children, but a child can have only one parent.
To find data stored in this model, the user needs to know the structure of the tree. Windows Registry is an example of a hierarchical database storing configuration settings and options on Microsoft Windows operating systems.
This model is similar to the Hierarchical Data Model. It is actually a subset of the network model. In the network model, data is stored in sets, instead of the hierarchical tree format. This solves the problem of data redundancy.
The set theory of the network model does not use a single-parent tree hierarchy. It allows a child to have more than one parent. Thus, the records are physically linked through linked-lists. For every database, a definition of the database name, record type for each record, and the components that make up those records is stored.
This is called its network schema. A portion of the database as seen by the application’s programs that actually produce the desired information from the data contained in the database is called sub-schema. It allows application programs to access the required data from the database. Raima Database Manager (RDM) Server by Raima Inc. is an example of a Network DBMS.
As the information needs grew and more sophisticated databases and applications were required, database design, management, and use became too cumbersome. This led to the development of what came to be called the Relational Model database.
The term ‘Relation’ is derived from the set theory of mathematics. In the Relational Model, unlike the Hierarchical and Network models, there are no physical links. All data is maintained in the form of tables consisting of rows and columns.
Data in two tables is related through common columns and not physical links. Operators are provided for operating on rows in tables. This model represents the database as a collection of relations.
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