Database Management System: DBMS Class Notes

Updated: Aug 18

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

  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 is database?

  2. What is the purpose of database?

  3. What are the drawbacks of using file system for storing data?

  4. What are the difference between typical file system and DBMS?

  5. What are the pros and cons of using DBMS?

  6. Explain various levels of abstraction present in DBMS?

  7. Differentiate between physical schema and logical schema.

  8. What do you understand by physical data independence?

  9. What is the instance in DBMS?

  10. Define database management system.

  11. Define schema.

  12. What are the functions of DBMS?

  13. What are the characteristics of DBMS?

  14. What are the components of DBMS?

  15. Write a short note on DBMS users.

  16. What is database constraints?

  17. What are the different types of languages that are present in DBMS?


Database Management System


Question 1 - What is database?

Answer - Database is a collection of interrelated data. These databases can be stored in the form of tables. A database can be of any size and varying complexity. A database may be generated and manipulated manually or it may be computerized.

 

Question 2 - What is the purpose of database?

Answer - In order to overcome the limitation of a file system, a new approach was required. Hence a database approach emerged. A database is a persistent collection of logically related data. Database can easily manage and update data. A database is compact, fast and accurate and much better than file system.

 

Question 3 - What are the drawbacks of using file system for storing data?

Answer - Drawbacks of file systems are are:

  1. Data redundancy and inconsistency: The same information may be written in several files. This redundancy leads to higher storage and access cost. It may lead to inconsistency.

  2. Difficulty in accessing data: The conventional file processing system do not allow data to retrieved in a convenient and efficient manner according to user choice.

  3. Data isolation: Because data are scattered in various file and files may be in different formats with new application programs to retrieve the appropriate data is difficult.

  4. Integrity Problems: Developers enforce data validation in the system by adding appropriate code in the various application program. How ever when new constraints are added, it is difficult to change the programs to enforce them.

  5. Atomicity: It is difficult to ensure atomicity in a file processing system when transaction failure occurs due to power failure, networking problems etc.

  6. Concurrent access: In the file processing system it is not possible to access a same file for transaction at same time

  7. Security problems: There is no security provided in file processing system to secure the data from unauthorized user access.

 

Question 4 - What are the difference between typical file system and DBMS?

Answer -

  1. In file system searching retrieving and accessing of data is difficult. In DBMS these operations are user friendly.

  2. In file system there is no standard format of data. In DBMS due to centralized system format of same type of data remain same.

  3. In file system there is no or very less security. In DBMS there is very high level of security,

  4. File system has more data redundency. DBMS has very low or no data redundancy.

  5. In file system data is isolated. In DBMS data can be shared.

  6. There is chances of inconsistency in file system. DBMS is consistent.

 

Question 5 - What are the pros and cons of using DBMS?

Answer - PROs:

  1. Reduction of redundancies: Avoids unnecessary duplication of data and effectively reduces the total amount of data storage required avoiding duplication in the elimination of the inconsistencies that tend to be present in redundant data files.

  2. Sharing of data: A database allows the sharing of data under its control by any number of application programs or users.

  3. Data Integrity: Data integrity means that the data contained in the database is both accurate and consistent.

  4. Data Security: The DBA who has the ultimate responsibility for the data in the DBMS can ensure that proper access procedures are followed including proper authentication schemas for access to the DBS and additional check before permitting access to sensitive data.

  5. Conflict resolution: DBA resolve the conflict on requirements of various user and applications. The DBA chooses the best file structure and access method to get optional performance for the application.

CONs:

  1. DBMS software and hardware (networking installation) cost is high

  2. The processing overhead by the DBMS for implementation of security, integrity and sharing of the data.

  3. centralized database control.

  4. Setup of the database system requires more knowledge, money, skills, and time.

  5. The complexity of the database may result in poor performance.

 

Question 6 - Explain various levels of abstraction present in DBMS?

Answer -

  1. External level abstraction: The external level is at the highest level of database abstraction . At this level, there will be many views define for different users requirement.

  2. Conceptual level: The conceptual schema hides the details of physical storage structures and concentrate on describing entities , data types, relationships, user operations and constraints.

  3. Internal level: This is a lowest level, which describes how the data is actually stores and describes the data structures and access methods to be used by the database.

levels of abstraction in dbms
Levels of Abstraction

 

Question 7 - Differentiate between physical schema and logical schema.

Answer -

  1. Physical Schema: It shows actual storage of data and its storage forms like memory/disc. It is the implementation of the data structure.

  2. Logical schema: It is more like definition of the data structure. It defines tables ,views and integrity constraints.

 

Question 8 - What do you understand by physical data independence?

Answer - Physical data independence is the ability to modify the physical scheme without making it necessary to rewrite application programs. Such modifications include changing from unblocked to blocked record storage, or from sequential to random access files.

 

Question 9 - What is the instance in DBMS?

Answer - The data or instance stored at particular moment in DBMS is called instance. Instance can change frequently.

 

Question 10 - Define database management system.

Answer - It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.

 

Question 11 - Define schema.

Answer - A schema is a logical data base description and is drawn as a chart of the types of data that are used . It gives the names of the entities and attributes and specify the relationships between them.

 

Question 12 - What are the functions of DBMS?

Answer -

  1. Defining database schema: it must give facility for defining the database structure also specifies access rights to authorized users.

  2. Manipulation of the database: The DBMS must have functions like insertion of record into database updation of data, deletion of data, retrieval of data.

  3. Sharing of database: The DBMS must share data items for multiple users by maintaining consistency of data.

  4. Protection of database: It must protect the database against unauthorized users.

  5. Database recovery: If for any reason the system fails DBMS must facilitate data base recovery.

 

Question 13 - What are the characteristics of DBMS?

Answer - Characteristics of DBMS are:

  1. Represents complex relationship between data.

  2. Controls data redundancy.

  3. Data Sharing.

  4. Enforce user defined rules.

  5. Backup and recovery facility.

  6. Different interfaces to manipulate data.

  7. Data independence and efficient access.

  8. Data integrity and security.

  9. Control over concurrency and data redundancy.

  10. Data Consistency.

 

Question 14 - What are the components of DBMS?

Answer - Components of DBMS are:

  1. Hardware: Here hardware means computer, hard disks, I/O devices etc that helps the data to store into memory.

  2. Software: It is the program that controls the whole function of DBMS.6.Users: People who involve in designing ,maintaining and use of DBMS.

  3. Data: DBMS exists to collect, store, process and access data, the most important component. The database contains both the actual or operational data and the metadata.

  4. Procedures: These are the general rules and instructions to design , manage and use DBMS.

  5. Database Access Language: Database Access Language is a simple language designed to write commands to access, insert, update and delete data stored in any database.

 

Question 15 - Write a short note on DBMS users.

Answer - DBMS users are divided into different categories:

  1. Naive users: Users who need not be aware of the presence of the database system or any other system supporting their usage are considered naïve users . A user of an automatic teller machine falls on this category.

  2. Online users: These are users who may communicate with the database directly via an online terminal or indirectly via a user interface and application program. These users are aware of the database system and also know the data manipulation language system.

  3. Application programmers: Professional programmers who are responsible for developing application programs or user interfaces utilized by the naïve and online user falls into this category.

  4. Database Administration: A person who has central control over the system is called database administrator.

 

Question 16 - What is database constraints?

Answer - databases has some conditions that must hold for it to be a valid relation. These conditions are called constraints. There are mainly three constraints −

  1. Key constraints

  2. Domain constraints

  3. Referential integrity constraints

 

Question 17 - What are the different types of languages that are present in DBMS?

Answer - 1. Data Definition language (DDL): DDL is used to define database objects .The conceptual schema is specified by a set of definitions expressed by this language. The result of DDL statements will be a set of tables that are stored in special file called data dictionary. Examples of DDL commands:

Create: It is used to create objects in the database.

Alter: It is used to alter the structure of the database.

Drop: It is used to delete objects from the database.


2. Data manipulation language (DML): A DML is a language that enables users to access or manipulate data stored in the database. Data manipulation involves retrieval of data from the database, insertion of new data into the database and deletion of data or modification of existing data.

Examples of DML commands:

Select: It is used to retrieve data from a database.

Insert: It is used to insert data into a table.

Update: It is used to update existing data within a table.

Delete: It is used to delete all records from a table.


3. Data control language (DCL): This language enables user to grant authorization and cancelling authorization of database objects.




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