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✅ DBMS Interview Questions Theory Based DBMS Interview Questions
1. What is database?
Ans: A information may be a logically coherent assortment of information with some inherent that means, representing some facet of globe and that is meant, designed and inhabited with information for a selected purpose.
2. What is DBMS?
Ans: It is a set of programs that permits user to form and maintain a info. In alternative words its general computer code that has the users with the processes of shaping, constructing and manipulating the info for numerous applications.
3. What is a Database system?
Ans: The database and DBMS software together is called as Database system.
4. What are the advantages of DBMS?
Ans: 1. Redundancy is controlled.
2. Unauthorized access is restricted.
3. Providing multiple user interfaces.
4. Enforcing integrity constraints.
5. Providing backup and recovery.
5. What are the disadvantages in File Processing System?
Ans:
● Data redundancy and inconsistency.
● Difficult in accessing data.
● Data isolation.
● Data integrity.
● Concurrent access is not possible.
● Security Problems.
6. Describe the three levels of data abstraction?
Ans: There are three levels of abstraction:
1. Physical level: The lowest level of abstraction describes how data are stored.
2. Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
3. View level: The highest level of abstraction describes only part of entire database.
7. Define the "integrity rules"?
Ans: There are two Integrity rules.
1. Entity Integrity: States that "Primary key cannot have NULL value"
2. Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation.
8. What is extension and intension?
Ans: 1. Extension: It is the number of tuples present in a table at any instance. This is time dependent.
2. Intension: It is a constant value that gives the name, structure of table and the constraints laid on it.
9. What is System R? What are its two major subsystems?
Ans: System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system.
Its two subsystems are:
I. Research Storage
II. System Relational Data System.
10. How is the data structure of System R different from the relational structure?
Ans: Unlike Relational systems in System R:
1. Domains are not supported
2. Enforcement of candidate key uniqueness is optional
3. Enforcement of entity integrity is optional
4. Referential integrity is not enforced
11. What is Join?
Ans: An SQL Join is used to combine data from two or more tables, based on a common field between them. For example, consider the following two tables.
Student Table
ENROLL NO STUDENT NAME ADDRESS
1000 geek1 geeksquiz1
1001 geek2 geeksquiz2
1002 geek3 geeksquiz3
Student Course Table
COURSE ID ENROLL NO
1 1000
2 1000
3 1000
1 1002
2 1003
Following is join query that shows names of students enrolled in different courseIDs.
SELECT StudentCourse.CourseID, Student.StudentName
FROM StudentCourse
INNER JOIN Customers ON StudentCourse.EnrollNo = Student.EnrollNo
ORDER BY StudentCourse.CourseID;
The above query would produce following result.
COURSEID STUDENTNAME
1 geek1
1 geek2
2 geek1
2 geek3
3 geek1
12. What is a view in SQL? How to create one
Ans: A view is a virtual table based on the result-set of an SQL statement. We can create using create view syntax.
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition
13. What is the Query to find 2nd highest salary of an employee?
Ans: SELECT max(salary) FROM EMPLOYEES WHERE salary IN
(SELECT salary FROM EMPLOYEEs MINUS SELECT max(salary) FROM EMPLOYEES);
OR
SELECT max(salary) FROM EMPLOYEES WHERE
salary <> (SELECT max(salary) FROM EMPLOYEES);
14. Get employee details from employee table whose first name ends with 'n' and name contains 4 letters
Ans: Select * from EMPLOYEE where FIRST_NAME like ' n' (Underscores)
15. Get employee details from employee table whose first name starts with 'J' and name contains 4 letters
Ans: Select * from EMPLOYEE where FIRST_NAME like 'J ' (Underscores)
16. Get employee details from employee table whose Salary greater than 600000
Ans: Select * from EMPLOYEE where Salary >600000
17. Get employee details from employee table whose Salary less than 800000
Ans: Select * from EMPLOYEE where Salary <800000
18. Get employee details from employee table whose Salary between 500000 and 800000
Ans: Select * from EMPLOYEE where Salary between 500000 and 80000
☑ About DBMS :
A Database Management System (DBMS) is a software application that is used to manage data stored in a database. A database is a collection of data that is organized in a structured manner, and a DBMS is responsible for creating, maintaining, and manipulating that data.
A DBMS provides several functions that allow users to interact with the database, such as creating, updating, deleting, and retrieving data. It also provides mechanisms for enforcing data integrity, ensuring that the data stored in the database is accurate and consistent.
Some of the key features of a DBMS include:
Data Definition: A DBMS provides tools for defining the structure of the database, including tables, fields, and relationships between tables.
Data Manipulation: A DBMS provides tools for inserting, updating, and deleting data from the database, as well as for querying the database to retrieve specific data.
Data Security: A DBMS provides mechanisms for controlling access to the database, including authentication and authorization.
Backup and Recovery: A DBMS provides tools for backing up the database and recovering data in the event of a system failure or data corruption.
Concurrency Control: A DBMS provides mechanisms for managing concurrent access to the database, ensuring that multiple users can access the database simultaneously without interfering with each other.
There are several popular DBMSs available today, including Oracle, MySQL, Microsoft SQL Server, PostgreSQL, and MongoDB. Each DBMS has its own strengths and weaknesses, and the choice of a DBMS depends on factors such as the size and complexity of the database, the specific requirements of the application, and the available resources.
☑ Some general information about DBMS interviews.
A DBMS (Database Management System) interview typically focuses on assessing a candidate's knowledge and experience in managing data within a database system. Here are some common topics that may be covered in a DBMS interview:
Database architecture and design: You may be asked about different database models, normalization techniques, data structures, and database design principles.
SQL (Structured Query Language): Questions may be asked about SQL queries, data manipulation language (DML), data definition language (DDL), and other SQL concepts.
Database security and management: You may be asked about how to secure a database, how to manage user access, backup and recovery procedures, and other related topics.
Data modeling and database normalization: You may be asked about the different data modeling techniques, including conceptual, logical, and physical modeling, and how to normalize a database.
Data warehousing and business intelligence: You may be asked about data warehousing concepts, ETL (extract, transform, and load) processes, and how to design and implement a data warehouse.
NoSQL databases: You may be asked about NoSQL databases, their characteristics, and when they are used instead of traditional SQL #databases.
In addition to technical skills, DBMS interviews may also assess a candidate's communication skills, problem-solving abilities, and ability to work in a team environment.
It's a good idea to prepare for a DBMS interview by reviewing and practicing your technical skills, researching the company and their database environment, and practicing your communication and problem-solving skills. Good luck with your #interview!
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