FC0-U71 Data and Database Fundamentals Practice Question
A data analyst is working with a large dataset stored in a columnar database. She needs to retrieve only the customer name and total order amount for orders placed in the last 30 days. Which two actions are most appropriate for optimizing this query? (Choose two.)
⚠ Common exam trap
The trap here is assuming that SELECT * is efficient or that row-based indexing is the primary optimization for columnar databases, when column pruning and filtering are what matter most.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a SELECT statement that lists only the customer name and total order amount columns
In a columnar database, performance improves when queries read only the columns they need and filter rows as early as possible. Listing specific columns avoids reading unnecessary data, and a WHERE clause on the order date limits the rows scanned. Using SELECT *, relying on row-based indexes, or sorting before filtering do not provide the same benefits.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use SELECT * to ensure all columns are available for analysis
Why it's wrong here
Using SELECT * retrieves every column, which forces the columnar database to read all columns even though only two are needed. This increases I/O and memory usage, slowing the query. In a columnar system, selecting unnecessary columns defeats the purpose of columnar storage, so this action is counterproductive for the stated goal.
- ✗
Sort the result set by customer name before filtering
Why it's wrong here
Sorting the result set does not reduce the amount of data read from storage; it only changes the order of the output. Filtering should happen before sorting to reduce the rows that need to be sorted. This action does not optimize the query for a columnar database and may add unnecessary processing overhead.
- ✓
Use a SELECT statement that lists only the customer name and total order amount columns
Why this is correct
In a columnar database, data is stored by column rather than by row. Selecting only the needed columns allows the database to read just those columns, reducing I/O and improving performance. This is a best practice for columnar systems and directly supports the analyst's goal of retrieving only customer name and total order amount.
- ✓
Add a WHERE clause that filters orders based on the order date
Why this is correct
A WHERE clause that filters on the order date limits the rows processed to only those from the last 30 days. In a columnar database, this can also take advantage of partition pruning or zone maps if the data is sorted or partitioned by date. This reduces the amount of data scanned and speeds up the query.
- ✗
Create a row-based index on the order date column
Why it's wrong here
Row-based indexes are typical in row-oriented databases and are not the primary optimization technique for columnar databases. Columnar systems often use zone maps, min-max indexes, or partitioning instead. Adding a row-based index may not be supported or may not provide the expected benefit, so it is not the most appropriate action here.
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Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This FC0-U71 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the FC0-U71 exam.