Which of the following provides a correct relational algebra syntax to answer this question:

Retrieve the student id, first name, last name, and major for all students who have GPA higher than 2.4

Question

Which of the following provides a correct relational algebra syntax to answer this question:

Retrieve the student id, first name, last name, and major for all students who have GPA higher than 2.4

BlackTom AI · Accepted Answer

We start by understanding the relational algebra task: we need to retrieve four attributes (student_id, first_name, last_name, major) for students whose GPA is greater than 2.4. In relational algebra, this combines selection (σ) to filter based on a condition and projection (π) to choose the required attributes, in the proper order.

Option 1: σ GPA>2.4 (π student_id, first_name, last_name, major (STUDENT))
- This applies a projection first (π) to the STUDENT relation, yielding only the four attributes, and then attempts a selection on GPA>2.4, which is invalid because GPA is not present after projection. The order is incorrect and would lead to an error or meaningless result.

Option 2: σ GPA>2.4 (STUDENT)Xπ student_id, first_name, last_name, major(STUDENT)
- This expression uses a Cartesian product (X) between two subexpressions: a selection σ GPA>2.4 (STUDENT) and a projection π ... (STUDENT). However, to answer the question, we must retain only the attributes for students meeting the GPA condition, not combine with a separate projection of the same relation. The syntax also misplaces the projection argument and misuses the Cartesian product for this task. Overall, this is not the standard and correct relational algebra formulation for this query.

Option 3: π student_id, first_name, last_name, major (σ GPA>2.4 (STUDENT))
- This option first applies the selection σ GPA>2.4 to filter the STUDENT relation, then projects the four requested attributes. This matches the required steps: filter by GPA, then retrieve the specific columns. The attribute list in the projection is exactly the requested set.

Option 4: ρ GPA>2.4(STUDENT)
- The operator ρ denotes renaming, not selection or projection. This option would rename the relation to GPA>2.4(STUDENT), which has no bearing on filtering rows or selecting particular columns. It does not accomplish the retrieval task and changes the relation's name in a way that does not help obtain the required four attributes for the qualifying students.

In summary, the core ideas are: apply a selection to keep only students with GPA > 2.4, then project the desired attributes to present only student_id, first_name, last_name, and major. The remaining options either apply operations in the wrong order, misuse operations like Cartesian product or renaming, or do not select the needed attributes after filtering.

Which of the following provides a correct relational algebra syntax to answer this question: Retrieve the student id, first name, last name, and major for all students who have GPA higher than 2.4

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