Data Base System models or Types of DBMS

1. Hierarchical Model
2. Network Model
3. Relational Model

1. Hierarchical Model or HDMS:

One of the earliest database management system was based on the Hierarchical model. Here data can be organized in the form of free structure or level-by-level manner with one limitation that is "every sub node or child node should have only one parent node".

2.Network Model or NDBMS:

To overcome the problems proposed by the hierarchical data model, the network data model was developed. It is also known as communication oriented database management system. Cross communication is possible in NDBMS.

Here data can be organized in the form of tree structure or level by level manner with cross communication. It cannot provide proper query facility,so that we have to write big programs even for small operation.It is complex in structure.

3. Relational DBMS:

RDBMS are most important database system used in the software industry today. It was Exclusively used to establish the relation the relation ship between two-database objects. One of the database objects is one table.

The Relation ship may be

One - One
One - Many
Many - One
Many - Many

Entity-Relationship Model (E-R Model):

An Entity is nothing but an object, which is physically existed in the real world.

Example: car,computer, chair

An Object in the database is a table so that an entity is nothing but a table.

Every Entity contains characters specifies its attributes simply it is a column in the table.

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