The correct answer is that the query would run faster because the index reduces the number of rows to scan for the Department condition. An index on the Department column acts like a sorted lookup table, allowing the database engine to jump directly to the matching rows instead of performing a full table scan. This narrows the pool of rows that must then be checked against the Salary condition, dramatically improving access path efficiency without altering the result set. On the CompTIA ITF+ FC0-U61 exam, this concept tests your understanding of how indexes affect query performance as a core database optimization principle. A common trap is assuming an index always speeds up every query or changes the returned data—it does not; it only speeds up row retrieval. Remember the memory tip: “Indexes are shortcuts, not filters—they find rows faster, but they don’t change what you get.”
FC0-U61 Database Fundamentals Practice Question
This FC0-U61 practice question tests your understanding of database fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Network Topology
Refer to the exhibit. The query returns two rows. If the database had an index on the Department column only, how would the query execution be affected?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The query would run faster because the index reduces the number of rows to scan for Department.
Option A is correct because an index on the Department column allows the database engine to quickly locate rows matching the Department condition without scanning the entire table. This reduces the number of rows that need to be evaluated for the Salary condition, speeding up the query. The index does not affect the result set—it only improves access path efficiency.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The query would run faster because the index reduces the number of rows to scan for Department.
Why this is correct
The index narrows down to IT rows quickly, then filters on Salary, improving performance.
Related concept
Read the scenario before looking for a memorised answer.
✗
The query would return fewer rows because the index excludes the Salary condition.
Why it's wrong here
The index does not change the logic; the WHERE clause still filters both conditions.
✗
The query would return more rows because the index includes both columns.
Why it's wrong here
An index on Department alone does not include Salary; the result set is unchanged.
✗
The query would fail because the index conflicts with the SELECT *.
Why it's wrong here
Indexes do not cause failures; they are designed to optimize queries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the misconception that an index changes the query result set (rows returned) rather than just the execution speed, leading candidates to incorrectly choose options B or C.
Detailed technical explanation
How to think about this question
Under the hood, a B-tree index on Department stores sorted key values with pointers to the corresponding rows. The query optimizer uses this index to perform an index seek, retrieving only the rows where Department matches, then applies the Salary filter on that reduced set. In a real-world scenario, if the Department column has high cardinality (many distinct values), the index dramatically reduces I/O; if low cardinality (e.g., only 2 departments), the index may be less effective and a full table scan could be chosen by the optimizer.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Database Fundamentals — This question tests Database Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The query would run faster because the index reduces the number of rows to scan for Department. — Option A is correct because an index on the Department column allows the database engine to quickly locate rows matching the Department condition without scanning the entire table. This reduces the number of rows that need to be evaluated for the Salary condition, speeding up the query. The index does not affect the result set—it only improves access path efficiency.
What should I do if I get this FC0-U61 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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