Database Management Systems

A database for an online fashion company like New Trends must handle various types of information related to products, customers, transactions, and operations.
Entities represent real-world objects or concepts in the database.
Here are six possible entities that Varun can include in his application:
(i) Customers: Stores customer information such as name, contact details, address, login credentials, and order history.
(ii) Products: Contains details about garments such as product ID, name, category, size, color, price, and stock availability.
(iii) Orders: Maintains order details including order ID, customer ID, product IDs, quantities, date of purchase, and payment status.
(iv) Payments: Stores payment transactions, methods (credit card, UPI, COD), payment IDs, timestamps, and success/failure status.
(v) Inventory: Tracks stock levels, incoming shipments, and warehouse details to avoid stockouts and delays.
(vi) Reviews/Ratings: Collects customer feedback, product reviews, star ratings, and comments to enhance product visibility and trust.
These entities help organize, retrieve, and manage business data efficiently and support smooth operation of the e-commerce platform.

Databases play a vital role in managing massive volumes of sensitive and transactional data in the banking sector.
Two major applications include:
(i) Customer Account Management: Databases are used to store personal and account-related information such as account number, balance, transaction history, and identification documents.
This ensures easy retrieval and updating of data for day-to-day operations.
(ii) Transaction Processing Systems: Every financial transaction like deposit, withdrawal, fund transfer, or loan repayment is recorded in real-time using database systems.
These systems ensure accuracy, speed, and security during high-volume transactions.

A Database Management System (DBMS) is software that enables efficient storage, retrieval, and management of data in a structured way.
Two important characteristics of a DBMS are:
(i) Data Integrity: DBMS ensures accuracy and consistency of data through constraints, keys, and validation rules.
It avoids data duplication and maintains the correctness of data across multiple tables.
(ii) Data Security: DBMS provides controlled access to data using authentication and authorization mechanisms.
Only authorized users can access or modify data, ensuring confidentiality and protection from misuse.
These features make DBMS a powerful tool for data-driven applications in every domain.

In relational databases, the NOT NULL constraint is used to ensure that a particular column cannot be left empty.
When the NOT NULL constraint is applied to the Salary column, it guarantees that every record must have a value entered for salary.
This is crucial in cases where missing data would be unacceptable, such as financial records or unique identifiers.
- DEFAULT assigns a default value to a column if no value is provided but does not enforce non-blank entries.
- CHECK is used to validate values against a condition but does not prevent NULL values by itself.
- NOT BLANK is not a standard SQL constraint.
Hence, option (A) is the correct answer as it ensures the Salary column cannot be left blank.

Databases are customized according to the domain in which they are used.
- Education databases are designed to store academic records, attendance, grades, and personal information of students and staff.
- Hospital databases maintain patient details, medical history, prescriptions, and treatment records.
- Government databases are built to store information related to citizens, such as electoral rolls, identity records, and public services.
However, option (C) is incorrect.
A banking database application is used for managing customer accounts, transactions, loan processing, and financial records — not for managing medicine stocks.
Managing medical stock is a responsibility of hospital or pharmacy inventory databases, not banking systems.
Therefore, option (C) is factually incorrect in the context of database domains.

In a database environment, different roles are responsible for various tasks such as design, development, maintenance, and evaluation.
The System Analyst plays a key role in bridging the gap between end users and the technical team.
Their primary responsibility is to gather requirements from stakeholders and translate them into clear, technical specifications.
System analysts analyze user needs, evaluate feasibility, create requirement documentation, and help in system design.
They ensure the database system is user-friendly, efficient, and tailored to organizational goals.
Unlike a DBA who manages the database operations or programmers who write code, the system analyst focuses on requirement analysis and solution design.
Therefore, the correct answer is (C) System Analyst.

In relational databases, when the value of a specific field or attribute is unknown, undefined, or inapplicable, it is represented using the special marker NULL.
NULL is not the same as zero, empty string, or blank — it signifies the complete absence of a value.
This helps maintain the integrity of database operations by clearly distinguishing unknown or missing data from actual values.
SQL queries must handle NULL values carefully, as standard operators behave differently when NULL is involved.
For instance, comparison with NULL using equality will not return true — instead, IS NULL or IS NOT NULL should be used.
Thus, NULL serves as a placeholder for unknown or missing data in database systems.

In SQL, the ALTER command is used to make changes to the structure of an existing table.
This includes operations such as adding, deleting, or modifying columns.
To add a new column, the syntax is: ALTER TABLE table_name ADD column_name datatype.
- The INSERT command is used to add new rows (records), not columns.
- The UPDATE command is used to change data in existing rows.
- The MODIFY keyword is not valid in standard SQL for altering table structure; it is used in some dialects only for altering column properties, not for adding new columns.
Thus, to add a column, the correct and standard SQL command is ALTER.

In SQL, data types define the kind of data that can be stored in a column.
- CHAR(n) is a fixed-length character type.
- VARCHAR(n) is a variable-length character type.
- DATE is used to store calendar dates.
However, STR(n) is not a standard SQL data type — it may appear in other programming languages like Python (as "str"), but not in SQL syntax.
Hence, it is the incorrect or invalid option in the context of SQL data types.

SQL stands for Structured Query Language.
It is the standard language used for interacting with Relational Database Management Systems (RDBMS).
SQL allows users to create databases, define tables, insert, update, delete, and retrieve data efficiently.
Common SQL operations include SELECT, INSERT, UPDATE, DELETE, and JOIN.
It is declarative in nature, meaning you describe what result you want rather than how to get it.
SQL supports both Data Definition Language (DDL) and Data Manipulation Language (DML) functionalities.
Widely supported by systems like MySQL, PostgreSQL, Oracle, and MS SQL Server, SQL is a foundational tool for database administrators and developers.

In relational database models, the term relation refers to a table.
A table is a structured format where data is stored in rows and columns.
Each row (also called a tuple) represents a unique record, and each column represents an attribute or field of the record.
The relational model, introduced by E. F. Codd, treats every relation as a set of tuples with the same attributes.
Tables help maintain organized data with defined relationships through primary keys and foreign keys.
This tabular representation makes it easy to retrieve, manipulate, and maintain data efficiently in RDBMS systems.
So, a relation in this model is nothing but a table.

DBMS stands for Database Management System.
It is a software system that enables users to define, create, maintain, and control access to databases.
A DBMS provides an interface between the user and the data, ensuring data consistency, integrity, security, and efficient access.
It supports operations like data storage, retrieval, update, and administration.
Examples of popular DBMS software include MySQL, Oracle Database, PostgreSQL, and Microsoft SQL Server.
A well-designed DBMS helps reduce redundancy and improves data organization across applications and users.