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Quizizz Hack – School Cheats C 3 Https://Schoolcats.Net/Quizizz V ANSWERS V GAVE PLAYERS BOTS B Based On The Figure Above, Identify The Number Of Tuples That Will Be Returned By The Following Relational Algebra Query : 0 Type = ‘Saving’ (Account) 1.3 A F Write The Relational Algebra To List Student’s Number And Student’a Name Whose Age Is 20 Years Old Or

The correct answer and explanation is:

Here’s a structured explanation and the solution to your question:

Relational Algebra to List Students’ Number and Name Whose Age is 20

Relational algebra is a procedural query language that works on relations (tables). It uses operators to query and retrieve data.

To retrieve the Student’s Number and Name of those who are 20 years old, the relational algebra query is:

π_StudentNumber, StudentName (σ_Age = 20 (Student))

Explanation:

  1. σ_Age = 20 (Student):
    • σ (Selection operator) is used to filter rows based on a condition.
    • Here, it selects rows where the age of students is 20 from the Student relation (table).
  2. π_StudentNumber, StudentName:
    • π (Projection operator) is used to select specific attributes (columns).
    • This operation retrieves only the StudentNumber and StudentName from the filtered rows.
  3. Combination:
    • The result of the selection (σ) is passed into the projection (π) to output only the required columns for students aged 20.

Number of Tuples Returned

The number of tuples (rows) returned depends on how many students in the Student relation meet the condition Age = 20. For instance:

  • If there are 3 students aged 20, the query will return 3 tuples.

Detailed Explanation

Relational algebra forms the theoretical basis for relational databases like SQL. It uses a set of operators like selection (σ), projection (π), union, difference, Cartesian product, and join to manipulate and query relations (tables). In the given query, we aim to filter and retrieve specific information.

The problem specifies filtering students whose age is 20. This is accomplished using the selection operator (σ), which applies a condition on rows. Once the relevant rows are identified, the projection operator (π) extracts only the desired columns—StudentNumber and StudentName.

The query π_StudentNumber, StudentName (σ_Age = 20 (Student)) executes as follows:

  1. Selection:
    • Searches the Student table to find all rows where the Age attribute is exactly 20.
  2. Projection:
    • From the filtered rows, only the StudentNumber and StudentName attributes are extracted.

Relational algebra does not involve specific syntax but rather serves as a conceptual framework to understand data manipulation. When implemented in a database system, the above query would translate to SQL like:

SELECT StudentNumber, StudentName
FROM Student
WHERE Age = 20;

If the Student table has, for example, 3 entries where students are 20 years old, the query will return exactly 3 tuples. Thus, the outcome directly depends on the dataset.

Understanding relational algebra is critical for database design, optimization, and ensuring precise data retrieval in applications. It simplifies complex queries and enhances system performance when effectively used.

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