Give the terms for each of the following: a) Collection of logically related records. b) DBMS creates a file t

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Q. Give the terms for each of the following:

a) Collection of logically related records.

b) DBMS creates a file that contains description about the data stored in the database.

c) Attribute that can uniquely identify the tuples in a relation.

d) Special value that is stored when actual data value is unknown for an attribute.

e) An attribute which can uniquely identify tuples of the table but is not defined as primary key of the table.

f) Software that is used to create, manipulate and maintain a relational database.

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Concept understanding — Database Fundamentals

Database Fundamentals

Think of a database as a well-organised filing cabinet. In your daily life, you already manage small databases without realising it — your phone's contact list, the catalogue of a library, or even the list of students in a class register. Each of these is a collection of related information stored in a structured way so that you can find what you need quickly.

What Exactly Is a Database?

A database is a collection of related data that is stored and managed systematically. The key word here is related. A random pile of papers on a desk is not a database — but the same papers, sorted into folders with labels and a clear order, become one. The purpose of a database is to allow efficient storage, retrieval, modification, and deletion of data.

Note

A database is not the same as a spreadsheet. A spreadsheet is a single table meant for one person's use. A database is designed for multiple users, handles large volumes of data, and ensures that the data remains consistent even when many people access it at once.

Why Do We Need Databases?

Imagine a small business that keeps customer orders in a notebook. As the business grows, the notebook becomes impossible to manage — pages get lost, two customers might be given the same order number, and finding a specific order takes forever. A database solves all these problems.

Databases provide:

Centralised control — all data lives in one place, so everyone works with the same information
Data consistency — rules can be enforced (for example, an order must belong to a real customer)
Security — different users can be given different levels of access
Reduced redundancy — the same piece of information is not stored in multiple places unnecessarily
Data independence — the way data is stored can change without affecting how users view it

The Core Idea: Tables and Relationships

The most common type of database is the relational database. Think of it as a collection of tables, where each table stores information about one kind of thing.

A table is made up of rows and columns. Each column represents a field (a single piece of information, like a name or a date), and each row represents a record (one complete set of fields, like one customer's full details).

For example, a university might have a Student table with columns: Roll Number, Name, Date of Birth, and Course. Each row is one student.

The real power comes from relationships between tables. The same university might have a Course table and an Enrolment table. The Enrolment table links a student to a course using the student's roll number and the course code — without repeating all the student's details or all the course details. This is what makes a database efficient.

Important

The primary key is a column (or a set of columns) that uniquely identifies each row in a table. For the Student table, Roll Number is the primary key — no two students can share the same roll number. A foreign key is a column in one table that refers to the primary key of another table, creating the link between them.

Database Management System (DBMS)

A Database Management System is the software that lets you create, manage, and interact with a database. You do not directly touch the data files — the DBMS does that for you. Popular examples include MySQL, Oracle, and Microsoft Access.

The DBMS handles:

Data storage and retrieval — it decides how to physically store data on a disk
Query processing — when you ask for "all students born after 2005", the DBMS finds the answer
Transaction management — if two people try to book the last seat on a flight at the same time, the DBMS ensures only one succeeds
Backup and recovery — if the system crashes, the DBMS can restore the data

A Simple Example to Tie It Together

Consider a library. Without a database, the librarian keeps a card catalogue and a handwritten log of who has borrowed which book. With a database, there might be three tables:

Books (Book ID, Title, Author, ISBN, Shelf Number)
Members (Member ID, Name, Phone, Join Date)
Borrowing (Borrow ID, Book ID, Member ID, Issue Date, Return Date)

The Borrowing table uses the Book ID and Member ID to link the other two tables. To find out which books a particular member has, the DBMS looks up the Member ID in the Borrowing table, then finds the corresponding book titles from the Books table — all in a fraction of a second.

What You Should Remember

A database is not just a collection of data — it is a structured, managed, and related collection. The structure (tables, keys, relationships) is what makes it powerful. The DBMS is the tool that makes it usable. And the whole point is to store data once, keep it accurate, and retrieve it quickly whenever needed.

Note

In your exams, you will often be asked to identify tables, primary keys, foreign keys, and relationships from a given scenario. Always start by asking: What are the main "things" in this scenario? Each thing becomes a table. Then ask: How are these things connected? That connection becomes the foreign key.

This is pure vocabulary from the Database Concepts chapter: file, data dictionary (metadata), primary key, NULL, alternate key and RDBMS. The trick in (e) is remembering the key hierarchy — every attribute that can uniquely identify tuples is a candidate key; the one chosen becomes the primary key, and the ones not chosen are alternate keys.

Let's take each description and reason to the term:

a) Collection of logically related records → File.

The data hierarchy is: bit → byte → field (attribute) → record (tuple) → file → database. A set of records about the same kind of entity (all student records, all item records) is a file; in the relational model this is exactly what a table (relation) stores. (Note the contrast: a database is a collection of logically related data/files, while a file is a collection of logically related records — the word "records" pins the answer.)

b) A file created by the DBMS containing the description of the data stored in the database → Data dictionary.

Data about data is metadata, and the DBMS keeps it in the data dictionary (also called the system catalog): table names, attribute names and types, constraints, keys. When you run DESC Student; in MySQL, the answer comes from the data dictionary.

c) Attribute that can uniquely identify the tuples in a relation → Primary key.

The attribute (or minimal set of attributes) designated to uniquely identify every tuple. It can never be NULL and never repeat — that is the entity integrity rule.

d) Special value stored when the actual data value is unknown for an attribute → NULL.

NULL is not zero and not an empty string — it is a marker meaning unknown, not applicable, or not yet available.

e) Attribute which can uniquely identify tuples but is not defined as the primary key → Alternate key.

All attributes capable of unique identification are candidate keys. One candidate key is promoted to primary key; every remaining candidate key is an alternate key. Example: in STUDENT(RollNo, AadhaarNo, Name), both RollNo and AadhaarNo are candidate keys; if RollNo is made primary, AadhaarNo is the alternate key.

f) Software used to create, manipulate and maintain a relational database → RDBMS.

A Relational Database Management System — MySQL, PostgreSQL, Oracle, SQLite are real examples.

✓Final answer

a) File (a table/relation in a relational database) \cdot b) Data dictionary (metadata) \cdot c) Primary key \cdot d) NULL \cdot e) Alternate key \cdot f) RDBMS — Relational Database Management System.

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2023Set 91/11 markMCQ
$Q. Fill in the blank. ............. is a number of tuples in a relation.$
(a) Attribute
(b) Degree
(c) Domain
(d) Cardinality
›Reveal solutionSolution

Cardinality is the term used for the number of tuples (rows) in a relation — it tells you how many records the table holds.

In database terminology, a relation is essentially a table. Each row in that table is called a tuple, and each column is called an attribute. When we talk about how many rows a relation contains, we are referring to its cardinality.

Think of a classroom register. If the register has 40 students listed, the cardinality of that register (as a relation) is 40. It is a count of the records present. This is a fundamental concept because it tells you the size of the data set you are working with — a high cardinality means many records, a low one means few.

The other options in the question are distinct concepts. An attribute is a column heading (like "Student Name" or "Roll Number"). The degree of a relation is the number of attributes (columns) it has, not the rows. A domain is the set of permissible values for a given attribute — for example, the domain for "Age" might be all positive integers up to 120.

Note

A common confusion is mixing up "degree" and "cardinality." A simple way to remember: degree counts columns (vertical), cardinality counts rows (horizontal).

So, when the question asks for "the number of tuples in a relation," the only correct term is cardinality. It is the row count, the record count, the measure of how many individual data entries the table holds.

Important

In relational databases, cardinality is a core property. It changes as you insert or delete rows, whereas the degree (number of columns) usually stays fixed once the table structure is defined.

✓Final answer
$In short, Cardinality is the number of tuples in a relation.$
CBSE 2023Set 91/41 markMCQ
$Q. Fill in the blank : In a relational model, tables are called _________, that store data for different columns.$
(a) Attributes
(b) Degrees
(c) Relations
(d) Tuples
›Reveal solutionSolution
In the relational model, tables are formally called relations — the foundational structure that organizes data into rows and columns.

The relational model, introduced by E.F. Codd in 1970, revolutionized how we think about organizing and managing data. At its heart lies a beautifully simple mathematical concept borrowed from set theory: the relation. When we work with databases today, we casually call them "tables," but the formal term that captures their essence is relation.

A relation is not just any collection of data. It is a structured entity with a specific schema — a set of attributes (the columns) and a collection of tuples (the rows) that conform to that schema. Think of it as a contract: every relation promises that its data will fit a particular shape, with each column representing a specific attribute and each row representing one complete record or tuple.

The terminology here is precise and worth understanding:

Attributes are the columns themselves — the individual properties or fields like "Student_ID," "Name," or "Marks." They define what kind of information each column holds.

Tuples are the rows — the actual data entries, each representing one complete instance (one student, one product, one transaction).

Degree refers to the number of attributes (columns) in a relation.

Relations are the tables as a whole — the complete structure that binds attributes and tuples together under a single name.

Note

The word "relation" comes from mathematics, where it describes a subset of a Cartesian product of domains. In simpler terms, a database relation is a table where every row is a valid combination of values from the allowed sets for each column.

When the question asks what tables are called in the relational model, it is asking for the formal name of the entire structure — not its parts. Attributes describe the columns, tuples describe the rows, and degree describes a count. Only relations describe the tables themselves.

✓Final answer
$In short, tables in the relational model are formally called relations — the answer is (c) Relations .$

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