Data Modeling: DBMS Class Notes

Updated: Aug 18

Mobiprep has created last-minute notes for all topics of Data Modeling to help you with the revision of concepts for your university examinations. So let’s get started with the lecture notes on Data Modelling.

  1. DBMS

  2. Data Modelling

  3. Database Architecture

  4. Relational Model

  5. Backup and Recovery

  6. Functional Dependencies

  7. Normalization

  8. Deadlock

  9. Transaction and Concurrency Control

  10. Files and Storage

  11. Relational Algebra

  12. Entity Relationship Model

  13. Indexing

Our team has curated a list of the most important questions asked in universities such as DU, DTU, VIT, SRM, IP, Pune University, Manipal University, and many more. The questions are created from the previous year's question papers of colleges and universities.

  1. What are data models?

  2. What are the different database models?

  3. Explain object relational database model.

  4. What is logical and physical designing?

  5. Explain entity relationship model.

  6. Explain relational database model with example.

  7. Explain hierarchical model with example.

  8. Explain network model with example.


Data Modeling


Question 1 - What are data models?

Answer - Data model is representation of

  1. Things (or entities or objects) of importance to a business or a system.

  2. How the things relate to each other. It is built and modified until it represents the structure well enough to write a system.

 

Question 2 - What are the different database models?

Answer - There are three types of data models:


1. Object Based Logical Models: These models can be used in describing the data at the logical and view levels. These models are having flexible structuring capabilities classified into following types.

  • The entity-relationship model.

  • The object-oriented model.

  • The semantic data model.

  • The functional data model

2. Record Based Logical Models: These models can also be used in describing the data at the logical and view levels. These models can be classified into:

  • Relational model.

  • Network model.

  • Hierarchal model.

3. Physical Models: These models can be used in describing the data at the lowest level (physical level). These models can be classified into

  • Unifying model

  • Frame memory model.

 

Question 3 - Explain object relational database model.

Answer - Object relational database model consist of classes, objects, inheritance etc. It is a combination of relational and object oriented database system. It allows its users to inherit objects, tables etc. Complex data types can be formed using existing data types in this type of models. Sometimes it is difficult to handle these types types of databases as they are very complex.

These models are having flexible structuring capabilities classified into following types.

  1. The entity-relationship model

  2. The object-oriented model

  3. The semantic data model

  4. The functional data model

 

Question 4 - What is logical and physical designing?

Answer - PHYSICAL DESIGNING

Physical database design is the process of choosing specific storage structures and access paths for the database files to achieve good performance for the various database applications. This step involves building indexes on some tables and clustering some tables. The physical database design can have the following options.

  1. Response Time: This is the elapsed time between submitting a database transaction for execution and receiving a response.

  2. Space Utilization: This is the amount of storage space used by the database files and their access path structures on disk including indexes and other access paths.

  3. Transaction Throughput: This is the average number of transactions that can be processed per minute.

LOGICAL DESIGNING

Under this, we must choose a DBMS to implement our database design and convert the conceptual database design into a database schema. The choice of DBMS is governed by number of factors as below.

  1. Economic Factor: Economic factors consists software acquisition cost, maintenance cost, hardware cost etc.

  2. Organizational Factors: Organizational factors consists of data complexity, sharing among applications, dynamically growing data etc.

 

Question 5 - Explain entity relationship model.

Answer - The entity-relationship data model perceives the real world as consisting of basic objects, called entities and relationships among these objects. It was developed to facilitate data base design by allowing specification of an enterprise schema which represents the overall logical structure of a data base.


Main features of ER-MODEL:

  1. Entity relationship model is a high level conceptual model

  2. It allows us to describe the data involved in a real world enterprise in terms of objects and their relationships.

  3. It is widely used to develop an initial design of a database.

  4. It provides a set of useful concepts that make it convenient for a developer to move from a base-id set of information to a detailed and description of information that can be easily implemented in a database system.

  5. It describes data as a collection of entities, relationships and attributes.


In the below diagram:

There are two entities Student and College and their relationship. The relationship between Student and College is many to one as a college can have many students however a student cannot study in multiple colleges at the same time. Student entity has attributes such as Stu_Id, Stu_Name & Stu_Addr and College entity has attributes such as Col_ID & Col_Name.



E-R Diagram in DBMS
E-R Diagram

 

Question 6 - Explain relational database model with example.

Answer - A relational database is a collection of one or more ‘relations’, where each relation is a table with rows and columns. This is the primary data model for commercial data processing applications. The major advantages of the relational model over the older data models are:

  1. It is simple and elegant.

  2. simple data representation.

  3. The ease with which even complex queries can be expressed. It concerned with three aspects of data:

  • Data structure ( tables)

  • Data integrity ( primary key rule, foreign key rule)

  • Data manipulation (Relational Operators)

  • Relational Algebra

  • Relational Calculus



relational database model in DBMS
Relational database model

 

Question 7 - Explain hierarchical model with example.

Answer - Hierarchical database model is the earliest database model. It looks like a tree data structure, a upside down tree. Data are related as parent child relationships i.e., p parent have many children but a child can have only one parent. This model structure allows the one-to-one and a one-to-many relationship between two or various types of data. This structure use physical order of data records in storage. The hierarchal model is not flexible because adding new relationships can result in wholesale changes to the existing structure, which in turn means all existing applications need to change as well.


ADVANTAGES

  1. Promotes data sharing

  2. Promote data integrity.

  3. Efficient with one to many relationships


DISADVANTAGES

  1. Navigation takes time

  2. Change in structure changes all application programs.

  3. Implementation is difficult

  4. Lacks structural independence



hierarchical model in DBMS
Hierarchical Model

 

Question 8 - Explain network model with example.

Answer - In network model data is organized like graph structure. Unlike hierarchical database it can have more than one parent. The network model differs from the relational model in that data are represented by collections of records, and relationships among data are represented by links. This database model was used to map many-to-many data relationships. There can be more than one path from previous node to next node. The operations of the network model are maintained by indexing structure of linked list (circular) where a program maintains a current position and navigates from one record to another by following the relationships in which the record participates.


ADVANTAGES:

  1. Data access if flexible

  2. Represents complex data better than hierarchical model.


DISADVANTAGES:

  1. Complex implementation

  2. Complex application programming.



network model in DBMS
Network Model




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