DBMS Interview Questions

In this session I am writing  Basic DBMS Interview Questions which are commonly asked in interview. Mostly these Questions  will ask in campus interviews as well as for Beginners.

1) What is DATABASE?

Ans:  A database is a collection of related information that is organized. It is a collection of tables,quires, reports and views and other objects. It can be easily accessed ,managed and update the data.

2) What is DBMS?

Ans:Here DBMS stands for Database Management System. It is a collections programs that designed to define,manipulate,retrieve and manage data in a database.

3) What is Database System?

Ans: If it contains both Database and DBMS software  is called as Database System. 

4) What are the advantages of DBMS?

Ans: 

• Redundancy is controlled.
• Unauthorized access is restricted.
• It provides multiple user interface.
• Main advantage is providing back up and recovery
• Enforcing Integrity Constraints
• It allows the user to perform complex transactions.
• It provides consistency,atomic,control concurrency
• It provides security

5)  What are the Disadvantage in file processing system?

Ans: 

• Data redundancy and inconsistency
• In this very difficult to accessing data
• Concurrent access is not possible
• Data isolation
• Data integrity
• Security problems

6) Describe three levels of data Abstraction?

Ans: There are three levels of abstraction. They are

Physical Level:  This is the lowest level of abstraction describes how data are stored.

Logical Level:  The next higher level of abstraction, describes what data are stored in database and what relationship among those data.

View Level: The highest level in data  abstraction, at this level users see the data in the form of rows and columns.

7)  What is Integrity and their rules?

Data Integrity refers accuracy and consistence of data. There are two integrity rules:

Entity integrity: It states that "primary key can not have NULL values"

Referential Integrity: It states that "Foreign key can be either a NULL value or should be Primary Key value of other relation.

8)  What is Data Independence?

Ans: It means that the application is independent of the storage structure and access strategy of data. In other words, The ability to modify the scheme definition in one level should not effect the schema definition in the next higher level. 

Physical Data Independence: If modification is done in physical level should not effect the logical level.

Logical Data Independence: If modification is done in logical level should not effect the view level.

9) What is normalization?

Ans: It a process of organizing the data in database to avoid data redundancy. It can minimize insertion,update and delete anomalies.

For more details about: Normalization tutorial

10)  What is an entity?

Ans : An entity is a thing or object  in the world with an independent existence.

11) What is an Entity Type?

Ans:  It is a collection of entities that have same attributes.

12) What is an Attribute?

Ans: It is a particular property,which describes the entity.

13) What is Primary Key?

Ans: A Primary Key is a column whose values uniquely identify every row in a table. That means Primary Key values can never be reused.

14) What is Data model?

Ans:  A collections of conceptual tools for describing data,data relationships data semantics and constraints. 

15) What is E-R model?

 Ans:  The data model is based on real world that consists of basic objects called entities  and of relationship among these objects.Entities are described in a database by a set of attributes.

16) What is functional Dependency?

Ans: A functional dependency is a  relationship between two attributes. Typically between the PK and other non-key attributes within the table. 

17)  What is RDBMS?

Ans:  RDBMS stands for Relational Data Base Management System. It is type of Data Base Management System(DBMS) that stores the data in the form of related tables. It is used to create,update and administer a relational database. 

18) How many types of relationships exists in database design?

Ans:  There are three main relationships models. They are

a) one-to-one
b)one-to-many
c)many-to-many

19) What is transaction?

Ans:  A transaction is a logical unit of database processing that includes one or more database operations. It is a program unit whose execution may or may not change the contents of the database

20) What is generalization?

Ans:  It is a process of extracting common characteristics from two or more classes and combining them into a generalized super class. So it is a bottom-up approach.  

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