Which one of the following actions will definitely not reduce any query cost?

Question

BlackTom AI · Accepted Answer

The question asks us to evaluate actions in terms of their impact on query cost. 
Option 1: 'Rewrite query to select all columns of a table instead of some particular columns' – this is typically detrimental to performance because it forces the database to read and return more data than necessary, increasing I/O, memory usage, and network transfer without providing additional value. Therefore, it will not reduce cost and often increases it.
Option 2: 'Rewrite query with parameters' – parameterized queries can help the database engine reuse execution plans and improve caching, which often reduces parsing and planning overhead and can lead to faster execution for repeated queries. This is generally a cost-reducing or cost-stabilizing practice.
Option 3: 'Create an index' – adding an index can dramatically reduce query cost by enabling faster data retrieval, especially for selective predicates, leading to lower I/O and quicker lookups.
Option 4: 'Store derived data' – materializing derived data (e.g., using a materialized view or cached results) can avoid expensive recomputation and reduce runtime cost for repeated queries.
In summary of the reasoning for each choice: increasing data retrieval by selecting all columns tends to increase cost, while parameterization, indexing, and derived data storage are common techniques that typically lower or stabilize query cost by improving plan reuse, access paths, or precomputing results. The analysis shows that the first option is the one that does not reduce cost and is, in most cases, detrimental to performance.

COMP90050_2025_SM2 Quiz 2

Which one of the following actions will definitely not reduce any query cost?

View Explanation

Log in for full answers

Similar Questions

Single Relation Plan A Compute the estimated result size for the query, and the reduction factor of each filter. 1: RF(establishmentYear) 2: RF(postcode) 3: Result Size (tuples)

Select all the options from the following that are steps or tasks of a query optimizer. You need to choose multiple options if they are the answers.

You have a user_table and a usage_details table. You want to find the rows corresponding to users who live in Nebraska (about 10% of all users) and join that subset with their usage details. Which of the following approaches is generally more efficient?

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler