Explain the The Database Model?

The types of the database models generally used in the business organizations can be categorized as follows –

1. Hierarchical Data Base Model (HDBM)

a. Is one of the earliest data base management systems.
b. This model has data logically as one to many relationship.
c. Follows a structured organizational mode.
d. Requires a controlled, finite and a rule based approach.
e. Represents data in a pyramidal or a tree like structure.
f. Each record appears to be like an organizational chart with one top level segment, called the root, spreading downwards into the branches and the leaves.
g. There is a record.
h. Within each record, the data elements are organized into the pieces of record which are referred to as the segments.
i. An upper segment is linked to a lower segment in a parent child relationship.
j. A parent segment may have more than one child.
k. A child can have only one parent.
l. The most common hierarchical data base management system has been the Information Management System (IMS) released by the IBM in the year 1968.

2. Network Data Base Model (NDBM)

a. Acts as the variation of the above Hierarchical Data Base Model.
b. This model has data logically as many–to– many relationship.
c. Helps in understanding and also helps in analyzing the sales Zone performance.
d. Analysis the sales and the recovery position.
e. Analysis the product wise sales performance.

3. Relational Database Model (RDBM)

a. Most recent of the three database models.
b. Was proposed by Dr. E.F Cod in the year 1970.
c. Consists of the data in the database as simple two dimensional tables called as the relations.
d. The table consists of the rows and also the columns.
e. Rows represent the individual records.
f. The columns represent the attributes of each of the record.
g. The information in more than one file can be easily extracted.
h. This information can be further combined to suit the user’s specific requirements.
i. The three basic operations of this model are Select, Project, Join.