DBMS Interview Questions & Answers for Freshers and Experienced
DBMS interview questions with answers covering normalization, indexing, transactions, SQL, and database design concepts.
Top DBMS Interview Questions for Freshers and Experienced Developers
Strengthen your database fundamentals with DBMS interview questions covering normalization, indexing, transactions, SQL queries, and real-world database design problems.
36 Questions2 PagesEasy · Medium · HardPage 1 of 2
1
What is database?
Answer
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.
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2
What is DBMS?
Answer
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.
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3
What are the advantages of DBMS?
Answer
Controlling Data Redundancy
Sharing of Data
Data Consistency
Integration of Data
Integration Constraints
Data Security
Report Writers
Backup and Recovery Procedures
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4
What are the disadvantage in File Processing System?
Answer
The file processing system has the following major disadvantages:
Data redundancy and inconsistency.
Integrity Problems.
Security Problems.
Difficulty in accessing data.
Data isolation.
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5
Define the "integrity rules" in DBMS?
Answer
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.
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6
What is primary, candidate and foreign keys in DBMS?
Answer
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.
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7
What is a super key?
Answer
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.
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8
What is the difference between primary key and unique constraints?
Answer
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.
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9
What is extension and intension in DBMS?
Answer
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.
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10
What is a view? How it is related to data independence in DBMS?
Answer
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.
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11
What is Data Model in DBMS?
Answer
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.
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12
What is E-R model in DBMS?
Answer
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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13
What is Object Oriented model in DBMS?
Answer
Object-oriented modeling (OOM) is the construction of objects using a collection of objects that contain stored values of the instance variables found within an object. Unlike models that are record-oriented, object-oriented values are solely objects.
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14
What is an Entity?
Answer
An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity.
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15
What is VDL (View Definition Language)?
Answer
It specifies user views and their mappings to the conceptual schema.
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16
What is SDL (Storage Definition Language)?
Answer
This language is to specify the internal schema. This language may specify the mapping between two schemas.
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17
What is DML (Data Manipulation Language)?
Answer
DML is abbreviation of Data Manipulation Language. It is used to retrieve, store, modify, delete, insert and update data in database. Examples: SELECT, UPDATE, INSERT statements. DDL is abbreviation of Data Definition Language. It is used to create and modify the structure of database objects in database.
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18
What is DML Compiler in DBMS?
Answer
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand. What is Query evaluation engine? It executes low-level instruction generated by compiler.
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19
What is normalization in DBMS?
Answer
Normalization is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anamolies. It is a multi-step process that puts data into tabular form by removing duplicated data from the relation tables.
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20
What is 1 NF (Normal Form)?
Answer
The domain of attribute must include only atomic (simple, indivisible) values.
