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DBMS Interview Questions and Answers

Those individuals who are looking for DBMS Interview Questions and Answers, they may check it from this page. Database Management System is one of the prerequisites part of IT Section. So Many contenders (Freshers and experienced) wish to get DBA Jobs in companies like TCS. But answering the DBMS Interview Questions is not a simple chore.

Well, there are assorted vacancies related to DBMS like Database Administrator, SQL Analyst etc. the selection procedure for almost all the vacancies are same, candidates need to face DBMS Interview Questions and Answers.

You Should Know This!!!

To help all the contenders in getting their vision job we are providing some significant   DBMS Interview Questions and Answers. Candidates can also download these questions free in PDF format via online mode by using the link given.

For getting more details about DBMS Interview Questions and Answers, go through this entire page which is well designed by the team members of www.privatejobshub.in

DBMS Interview Questions and Answers

DBMS Interview Questions and Answers for Freshers:

Ques 1: What is database?

Ans. – A database is a collection of information that is organized. It represents the data into information i.e. after processed and give a meaning of it using different attribute which connecting it to real world entity.

Ques 2: What is DBMS?

Ans. – DBMS stands for Database Management System. DBMS is an application providing an environment to retrieve and manipulate the database. Database Management System as name implies it manages the database and consist different operation on it like creating database, updating database, creating or deleting tables, searching and organizing the data into databases, etc.

Ques 3: What are advantages of DBMS over traditional file based systems?

Ans: Database management systems were developed to handle the following difficulties of typical file-processing systems supported by conventional operating systems.
  • Data redundancy and inconsistency
  • Difficulty in accessing data
  • Data isolation – multiple files and formats
  • Integrity problems
  • Atomicity of updates
  • Concurrent access by multiple users
  • Security problems
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Ques 4: What is Lossless join property?

Ans. –It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

Ques 5: Why DBMS is better over File System Processing?

Ans. – File system having the following disadvantages – 
  • Redundancy problem
  • Inconsistency
  • Data isolation
  • Data integrity
  • No security
  • No concurrent access
Ques 6: Explain three levels of Abstraction?

Ans. – Abstraction is usually defining the important feature of system hiding the complexity of it. Three levels are –
  • Physical level: lowest level of abstraction, describes how data is stored
  • Logical level: next level to physical level of abstraction, in this level only data and its relationship is defined.
  • View level: highest level of abstraction, describes only part of database.
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Ques 7: What is normalization?

Ans. – Normalization is a methodology by which DBMS minimizes redundancy and also minimizes the insertion and deletion anomalies. It achieves such process of analysis based on the functional dependencies.

Ques 8: What is E-R model?

Ans. –Entity Relation model consists of real world objects i.e. entities and defines the relationships among these entities. Set of attributes defines an entity.

Ques 9: What is DML?

Ans. – DML (Data Manipulation Language) facilitate the user to manipulate the data in the database. In Procedural DML user have to describe what data is to manipulate and how to do it. Whereas in non-procedural DML user only have to describe which data has to get without specifying how to do it.


Ques 10: What is DML compiler?

Ans. –It translates the query language into low level instruction that a query evaluation engine can understood.

Ques 11: What are super key, primary key, and candidate key?

Ans. –A super key is a set of attributes of a relation schema upon which all attributes of the schema are functionally dependent. Primary key is one of the candidate keys that uniquely define each and every record in table. Candidate key is a minimal super key that uniquely defining the every record.

Ques 12: What is the main difference between primary and unique key?

Ans. –Primary key doesn’t contain NULL but unique constraint contains it.


Ques 13: Differentiate between DBMS and RDBMS?

Ans. –DBMS provides the organized database with managing, retrieving, updating tools and operations that can be performed on databases. RDBMS also provide these functionalities with relationship integrity.

Ques 14: What is Functional Dependency?

Ans. – Functional Dependency is the starting point of normalization. Functional Dependency exists when a relation between two attributes allows you to uniquely determine the corresponding attributes value.

Ques 15: Did you heard about the sixth normal form?

Ans. –If we want relational system in concurrence with time we use sixth normal form.


Ques 16: List out some DDL and DML commands?

Ans. – DDL commands are Create, Alter and Drop. DML commands are basically four commands that are – Select, Update, Insert, Delete.

Ques 17: What is like operator for?

Ans. –Like operator is used to match the pattern that have to search in a database / table / record / field.

Ques 18: What is order by clause?

Ans. – Order by clause is used to sort the data either in the ascending order or in the descending order.


Ques 19: What are different types of joins?

Ans Inner join: Used when information of entity should be check that matched in both tables.
  • Left outer join: It shows all records from left table and the entity matching with right table will show from right table otherwise puts null.
  • Right outer join: it is opposite to left outer join and shows all records of right table.
Ques 20: What is Cross Join or Cartesian product?

Ans. –It combines all the records from both tables. The size of resultant table or total records of cross table is equals to the product of number of records in the both tables.

Ques 21: What is View?

Ans. –View is the virtual table that is implemented on the basis of the result set returned by the select command.


Ques 22:  What is difference between SQL and SQL SERVER?

Ans. –SQL is a language that provides an interface to RDBMS, developed by IBM. SQL SERVER is a RDBMS just like Oracle, DB2.

Ques 23:  What is Specialization?

Ans. –It is the process of defining a set of subclasses of an entity type where each subclass contain all the attributes and relationships of the parent entity and may have additional attributes and relationships which are specific to itself.

Ques 24:  What is generalization?

Ans. –It is the process of finding common attributes and relations of a number of entities and defining a common super class for them.

Ques 25: What is meant by Proactive, Retroactive, and Simultaneous Update?

Ans. –Proactive Update: The updates that are applied to database before it becomes effective in real world.
  • Retroactive Update: The updates that are applied to database after it becomes effective in real world.
  • Simultaneous Update: The updates that are applied to database at the same time when it becomes effective in real world.
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Ques 26: What is RAID Technology?

Ans. –The main goal of raid technology is to even out the widely different rates of performance improvement of disks against those in memory and microprocessor. Raid technology employs the technique of data striping to achieve higher transfer rates.

Ques 27:  What are serial, non serial schedule?

Ans. –A schedule S is serial if, for every transaction T participating in the schedule, all the operations of T is executed consecutively in the schedule, otherwise, the schedule is called non-serial schedule.


Ques 28:  What are conflict serializable schedules?

Ans. –A schedule S of n transactions is serializable if it is equivalent to some serial schedule of the same n transactions.

Ques 29:  What is view serializable?

Ans. –A schedule is said to be view serializable if it is view equivalent with some serial schedule.

DBMS Technical Interview Questions:

Ques1: 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

ENROLLNO
STUDENTNAME
ADDRESS
1000
geek1
geeksquiz1
1001
geek2
geeksquiz2
1002
geek3
geeksquiz3


Student Course Table

COURSEID
ENROLLNO
1
1000
2
1000
3
1000
1
1002
2
1003

Following is join query that shows names of students enrolled in different course IDs.

SELECT Student Course. Course ID, Student. Student Name

       FROM Student Course
       INNER JOIN Customers
       ON Student Course Enroll No = Student. Enroll No
       ORDER BY Student Course. Course ID

The above query would produce following result.

COURSEID
STUDENTNAME
1
geek1
1
geek2
2
geek1
2
geek3
3
geek1


Ques2: 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
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Ques3. There is a table where only one row is fully repeated. Write a Query to find the repeated row

Name
Section
abc
CS1
bcd
CS2
abc
CS1

In the above table, we can find duplicate row using below query.
SELECT name, section FROM tbl
GROUP BY name, section
HAVING COUNT(*) > 1

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