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dbms Interview Questions and Answers

Each dbms Interview Question Sets contains 12 questions.

1)   What is database?

A database is a collection of information that is organized so that it can easily be accessed, managed, and updated. In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images.

2)   What is DBMS?

A database management system (DBMS) is system software for creating and managing databases. The DBMS provides users and programmers with a systematic way to create, retrieve, update and manage data.

3)   What are the advantages of DBMS?

Controlling Data Redundancy
Sharing of Data
Data Consistency
Integration of Data
Integration Constraints
Data Security
Report Writers
Backup and Recovery Procedures

4)   What are the disadvantage in File Processing System?

The file processing system has the following major disadvantages:
Data redundancy and inconsistency.
Integrity Problems.
Security Problems.
Difficulty in accessing data.
Data isolation.

5)   Define the "integrity rules" in DBMS?

There are two Integrity rules.
Entity Integrity: States that "Primary key cannot have NULL value"
Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation.

6)   What is primary, candidate and foreign keys in DBMS?

Primary Key: The attribute or combination of attributes that uniquely identifies a row or record in a relation is known as primary key.
Candidate Key or Alternate key: A relation can have only one primary key. It may contain many fields or combination of fields that can be used as primary key. One field or combination of fields is used as primary key. The fields or combination of fields that are not used as primary key are known as candidate key or alternate key.
Foreign Key:A foreign key is an attribute or combination of attribute in a relation whose value match a primary key in another relation. The table in which foreign key is created is called as dependent table. The table to which foreign key is refers is known as parent table.

7)   What is a super key?

A superkey is a combination of attributes that can be uniquely used to identify a database record. A table might have many superkeys. Candidate keys are a special subset of superkeys that do not have any extraneous information in them.

8)   What is the difference between primary key and unique constraints?

1.Primary Key constraints are not nullable. UNIQUE constraints may be nullable.
2.When you create a UNIQUE constraint, the database automatically creates a UNIQUE index. For MS SQL Server databases, a PRIMARY KEY will generate a unique CLUSTERED INDEX.

9)   What is extension and intension in DBMS?

Extension: It is the number of tuples present in a table at any instance. This is time dependent.
Intension: It is a constant value that gives the name, structure of table and the constraints laid on it.

10)   What is a view? How it is related to data independence in DBMS?

In a database management system, a view is a way of portraying information in the database. Often thought of as a virtual table, the view doesn't actually store information itself, but just pulls it out of one or more existing tables.

11)   What is Data Model in DBMS?

A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model, which uses a table-based format.

12)   What is E-R model in DBMS?

An entity relationship model, also called an entity-relationship (ER) diagram, is a graphical representation of entities and their relationships to each other, typically used in computing in regard to the organization of data within databases or information systems.

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