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# Relational Algebra Quiz

Created by
@OticPrudence9241

### What is the main function of filters in relational algebra?

To filter attributes/columns of a resulting relation

### What is a characteristic of relational algebra?

Non-commutative and procedural

### What is the purpose of the 'select' clause in relational algebra?

To project specific attributes from a relation

### What is the notation for the select operation in relational algebra?

<p>σcondition(relation)</p> Signup and view all the answers

### What is the result of applying the select operation to a relation?

<p>A relation with less attributes or tuples than the original</p> Signup and view all the answers

### What is the purpose of the projection operation in relational algebra?

<p>To project specific attributes from a relation</p> Signup and view all the answers

### What is an example of a query in relational algebra?

<p>Show all first and last names of employees.</p> Signup and view all the answers

### What is the input to relational algebra operations?

<p>Relations</p> Signup and view all the answers

### What is the symbol used to represent the selection operation in relational algebra?

<p>σ</p> Signup and view all the answers

### What is the purpose of the 'where' clause in relational algebra?

<p>To filter tuples based on a condition</p> Signup and view all the answers

### What is the result of the selection operation on a relation?

<p>A relation with the same number of attributes but less tuples</p> Signup and view all the answers

### What is the purpose of the rename operation in relational algebra?

<p>To rename attributes in a relation</p> Signup and view all the answers

### What is the notation for the selection operation that shows all employees who belong to department number 5?

<p>σdepartment=5</p> Signup and view all the answers

### What is the combination of operations that normally happens in relational algebra?

<p>Selection and projection</p> Signup and view all the answers

## Study Notes

### Relational Algebra

• Relational algebra is a procedural language that represents a query in a mathematical way.
• Relations are the inputs, and resulting relations are the outputs.

### Select Operation (σ)

• The select operation filters the tuples of a resulting relation R based on the condition provided.
• It is commutative.
• Example: σcondition(relation)
• Example 1: Show all employees who belong to department number 5. σdepartment=5(employee)
• Example 2: Show all employees whose monthly salary is above Php30,000 and belong to department 3, 4, and 5. σsalary > 30000 and department >=3 and department

### Project Operation (π)

• The project operation filters the attributes/columns of a resulting relation R based on the attributes listed.
• It is not entirely commutative, but proper use of projection makes it commutative.
• Example: πattributes(relation)
• Example: Show all first and last names of employees. πfirstname, lastname(employee)
• Example 2: Show all last names, department numbers, and monthly salaries of employees. πlastname, department, salary(employee)

### Rename Operation (⍴)

• The rename operation renames a relation and/or its attributes.
• Example: ⍴new_relation(new_attributes)(old_relation)
• It is used to rename a relation and/or its attributes.

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## Description

This quiz covers the basics of Relational Algebra, including filtering attributes and columns, procedural language, and relation inputs.

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