UG-BCA-S2, Database Management Systems, First Internal Examination, February 2024

 

Section A

Answer any 5 questions. Each question carries 2 marks.

1.    Define database

A database is a structured collection of data that is organized and stored in a way that facilitates efficient retrieval and manipulation. It typically consists of tables or files that are interrelated and contain information such as records, fields, and relationships. Databases are used to store, manage, and retrieve data in a systematic and organized manner.

2. List out the DDL and DML commands

DDL commands:

CREATE: Used to create database objects like tables, indexes, or views.

ALTER: Modifies the structure of an existing database object.

DROP: Deletes a database object, such as a table or index.

TRUNCATE: Removes all records from a table, but retains the table structure.

COMMENT: Adds comments to the data dictionary.

DML commands:

SELECT: Retrieves data from one or more tables.

INSERT: Adds new records to a table.

UPDATE: Modifies existing records in a table.

DELETE: Removes records from a table.

3.What is an attribute in E R Diagram. Give an example

Attribute in E-R Diagram:

In an Entity-Relationship (E-R) Diagram, an attribute is a property or characteristic of an entity set. It describes the information that can be stored for each entity in the database. For example, if "Person" is an entity, then "Name" and "Age" could be attributes of that entity.

 

Example:

Entity: Person

Attributes:

Name (String)

Age (Integer)

Gender (String)

 

4. Compare primary key and candidate key

Primary Key:

Uniquely identifies each record in a table.

Cannot contain NULL values.

There can be only one primary key in a table.

It is chosen as the main identifier for the table.

Candidate Key:

A set of attributes that can uniquely identify a record.

Like a primary key, it must be unique and not contain NULL values.

A table may have multiple candidate keys.

One of the candidate keys is selected as the primary key

5. Define schema and instance with examples.

Schema:

A schema is a blueprint or structure that defines the organization of data in a database.

It defines tables, fields, relationships, and constraints.

Example: In a university database, the schema might include tables for students, courses, and instructors, along with relationships between them.

Instance:

An instance is a specific occurrence or set of data values at a particular point in time within a database.

It represents the actual data stored in the database.

Example: In the student table, an instance would be a specific student's information with their unique student ID, name, and other attributes.

6.  Define participation constraints in Entity model

Participation constraints in Entity model:

Participation constraints in an Entity-Relationship (ER) model define the level of participation of entities in a relationship.

Total Participation: Every entity in the entity set must participate in the relationship.

Partial Participation: Some entities in the entity set may not participate in the relationship.

Example:

Consider a relationship between "Department" and "Employee" entities.

Total Participation: Every department must have at least one employee (each department participates fully).

Partial Participation: A department may have no employees, but some departments have employees (some departments participate partially).

                                                                                     (5 x 2 =10 Marks)

Section B

Answer any 3 questions. Each question carries 5 marks.

7.    Explain Data Models.

A data model is a conceptual representation of how data is structured and organized within a database. It provides a way to describe the design and architecture of a database system. There are several types of data models, including:

HIGH LEVEL MODEL

REPRESENATIONAL MODEL

PHYSICAL MODEL

8.  Explain the characteristics of DBMS

a Security: Enforces access controls to ensure that only authorized users can access and modify data.

Data Integrity: Ensures the accuracy and consistency of data through constraints and validation rules.

Concurrency Control: Manages simultaneous access to the database to prevent data inconsistencies.

Query Language: Provides a language (e.g., SQL) for users to interact with the database and retrieve information.

Transaction Management: Supports transactions to ensure the atomicity, consistency, isolation, and durability (ACID properties) of database operations.

9. Write about constraints in relational model

Primary Key Constraint: Ensures that a column or a set of columns uniquely identifies each record in a table.

Foreign Key Constraint: Ensures referential integrity by linking a column or set of columns in one table to the primary key in another table.

Unique Constraint: Ensures that all values in a column or a set of columns are unique.

Check Constraint: Specifies a condition that must be true for each row in a table.

Default Constraint: Assigns a default value for a column if no value is provided during an insertion.

NotNull Constraint: Ensures that a column cannot have a NULL value

10. Explain mapping cardinalities in ER Model

Mapping Cardinalities in ER Model:

One-to-One (1:1): A single entity in one set is related to only one entity in another set, and vice versa. For example, a person having one passport and a passport being associated with one person.

One-to-Many (1:N): A single entity in one set is related to multiple entities in another set. For example, a department having multiple employees but each employee belonging to only one department.

Many-to-One (N:1): Multiple entities in one set are related to a single entity in another set. For example, multiple students attending the same course, but the course is taught by only one instructor.

Many-to-Many (N:N): Multiple entities in one set are related to multiple entities in another set. For example, students enrolling in multiple courses, and each course having multiple students.

                    (3 x 5 = 15 Marks)

Section C

Answer any 1 question. The question carries 15 marks

11.  Explain architecture of DBMS.

MENTION ALL USERS COMPONENTS USERS AND LABEL WITH A NEAT DIGRAM

12   Explain ER modelling in detail.

WRITE ABOUT ENTITY, ATTRIBUTE RELATIONSHIP AND CONSTRAINTS

                                                                                                               (1 X 15 = 15 Marks)