DBMS Unit-2: Relational Model Quiz

Questions and Answers

What was proposed by E.F. Codd to model data in the form of tables?

Hierarchical Model

Object-Oriented Model

Relational Model (correct)

Entity-Relationship Model

In a relational database, what term is used to describe the vertical component of a table?

Relation

Tuple

Row

Attribute (correct)

Which operator is used to retrieve specific rows from a table based on a condition?

Aggregation

Join

Projection

Selection (correct)

What is the term for the number of tuples in a relational database table?

Cardinality Signup and view all the answers

Which of the following describes the columns in a relational database?

Vertical components with specific data types Signup and view all the answers

How is the relational model fundamentally characterized?

Based on mathematical concepts of relations Signup and view all the answers

What does the term 'relation' refer to in the context of a relational database?

A database object that holds a collection of data for a specific topic Signup and view all the answers

Which operator in relational algebra is used to combine rows from two or more tables?

Cross Product Signup and view all the answers

What will be the result of projecting the Name and Branch of students with Branch ‘ME’ or ‘CI’?

Mitesh, ME and Nilesh, CI Signup and view all the answers

Which of the following relational algebra expressions will list the Name of students in the 'CE' branch?

σBranch='CE'(Student) Signup and view all the answers

How many tuples would be produced from the Cross Product of Student and Employee tables?

Variable based on Student and Employee counts Signup and view all the answers

Which students have an SPI greater than 8 and belong to the 'CE' branch?

No students fit this criteria Signup and view all the answers

What is the condition for listing students in the output with SPI between 7 and 9?

7 < SPI < 9 Signup and view all the answers

Which employees will have their names displayed if selecting from 'HR' department with salary above 20000?

Nilesh and Mayur Signup and view all the answers

Which expression correctly lists the employee names who belong to 'Admin' or 'HR' with salary more than 15000?

∏Name(σDept='HR' V Dept='Admin' V Salary > 15000(Employee)) Signup and view all the answers

What will be the output of projecting Name of employees from both 'HR' and 'Admin' departments?

Nilesh, Mayur, Hardik, Ajay Signup and view all the answers

Which student has a SPI greater than 8 and belongs to the CE branch?

Meet Signup and view all the answers

Which students are in either the CI or ME branch?

Mitesh and Nilesh Signup and view all the answers

What is the correct operation to display the details of students whose SPI is between 7 and 9?

σSPI>7 Λ SPI<9 (Student) Signup and view all the answers

Which command correctly retrieves the Name and Branch of students with SPI greater than 8?

∏ Name, Branch (σSPI>8 (Student)) Signup and view all the answers

What will be the output when displaying students with SPI greater than 8 using the combined projection and selection operation?

Mitesh, ME, 9 and Nilesh, CI, 9 Signup and view all the answers

To display the names of students belonging to either the ME or CI branch, which operation would you use?

∏ Name (σBranch='ME' V Branch='CI' (Student)) Signup and view all the answers

Which operation needs to be performed to get students with a SPI higher than 7 from the CE branch?

σBranch='CE' (σSPI>7 (Student)) Signup and view all the answers

Which student's SPI is the lowest among those mentioned?

Raju Signup and view all the answers

What does the cross product of the 'Student' and 'Result' relations include when considering the selected attributes?

All combinations of the selected attributes from both relations Signup and view all the answers

Which of the following attributes distinguishes the 'Student' and 'Result' relations when performing a cross product?

RNo Signup and view all the answers

If a cross product is performed between the 'Student' and 'Result' tables, what would be the output for RNo 101?

All combinations for RNo 101 and RNo 103 Signup and view all the answers

When selecting tuples from the 'Result' relation, which condition must be met based on the provided data?

SPI must be greater than 7 Signup and view all the answers

Which combination of attributes was used to filter the 'Student' relation in the example?

Branch = ‘CE’ and Sem = 3 Signup and view all the answers

In the Cartesian product example, what is the result's output format?

Result with merged columns from both relations Signup and view all the answers

What is the significance of using the notation ∏ RNo, Name, Branch (Student) X ∏ RNo, SPI, BL (Result)?

It limits the attributes included in the cross product. Signup and view all the answers

Which output attribute in the 'Result' relation is used to differentiate students who performed well?

Rank Signup and view all the answers

What term refers to the horizontal component of a table, consisting of a sequence of values for each column?

Row Signup and view all the answers

What is the degree of a table defined as?

The number of columns Signup and view all the answers

Which of the following best describes a domain in the context of databases?

A grouping of unique values possible for a specific column Signup and view all the answers

Which of the following statements accurately defines relational algebra?

An algebra whose operands are variables representing relations Signup and view all the answers

What elements are included in the mathematical system referred to as algebra?

Variables and operators Signup and view all the answers

Study Notes

Relational Model Overview

Proposed by E.F. Codd to represent data using relations or tables.
Utilizes mathematical concepts of relation; data is organized into tables (relations).
Tables consist of columns (attributes) and rows (tuples).
Unique naming for each column; data types include varchar, decimal, integer, datetime, etc.
Cardinality refers to the number of tuples in a table; degree indicates the number of columns.

Structure of Relational Databases

Table (Relation): Database object holding data on specific topics.
Row (Tuple/Record): Horizontal component in a table; represents a single record.
Column (Attribute): Vertical component with a unique name in a table.

Domains and Attributes

Domain: Set of all possible unique values for a specific column.
Example: Domain of the "Branch" attribute includes values (CE, CI, ME, EE).

Relational Algebra

Consists of operands (variables/values) and operators (symbols for procedures).
Operands in this context are relations or variables representing relations.
Operators are designed for common database operations, forming a query language.

Fundamental Operators in Relational Algebra

Selection (σ): Retrieves rows meeting specific conditions.
- Example: σBranch='CE' and SPI>8 returns records for students in CE branch with SPI greater than 8.
Projection (π): Chooses specific columns from a table.
- Example: πName, Branch, SPI selects only the Name, Branch, and SPI columns.

Combined Selection and Projection

Combining selection and projection allows for detailed queries.
Example: To find names, branch, and SPI of CE students with SPI > 7, use combined operations.

Cartesian Product (Cross Product)

Symbolized as X; combines every tuple of one relation with every tuple of another.
The number of tuples in the result equals the product of the number of tuples in the two relations.
Attributes of the resulting relation equal the sum of the attributes in both relations.

Examples of Cartesian Product

Output includes every combination of selected attributes from involved relations.
Example: Performing a cross product between the Student and Result tables shows data combinations.

Additional Relational Algebra Exercises

Queries can be formed simply by writing relational algebra expressions to filter or select specific records based on various conditions.
Examples include selecting students from certain branches or filtering employees from specific departments with certain salary requirements.

Application in Employee Table

Similar techniques apply to different tables like Employee, where selection conditions can filter based on department and salary.

These concepts are foundational for understanding and using database management systems effectively, particularly when dealing with relational databases.

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Description

Test your knowledge of the Relational Model in Database Management Systems. This quiz covers fundamental concepts such as relational algebra, operators, and both open source and commercial DBMS options. Prepare yourself to demonstrate your understanding of database structures and operations.