mediumMultiple ChoiceObjective-mapped
Database Index: Speed Up SELECT Queries on Large Tables
A company's database administrator notices that queries against a large customer table are running slowly. The table has millions of rows and is frequently filtered by the 'last_name' column. Which of the following is the BEST way to improve query performance without changing the application code?
Quick Answer
The correct answer is to create an index on the 'last_name' column. This works because a database index functions like a book’s index, allowing the database engine to locate rows that match a filter condition without performing a full table scan across millions of rows. By reducing the number of disk reads and CPU cycles needed for each query, an index directly improves database index query performance on large tables. On the CompTIA ITF+ FC0-U61 exam, this concept tests your understanding of how indexes optimize SELECT operations without altering application code—a common scenario in database administration. A frequent trap is assuming that adding more indexes always helps, but remember that indexes speed up reads while slightly slowing writes. For this exam, think of the mnemonic “INDEX = Instant Data EXtraction” to recall that indexes are the go-to solution for accelerating filtered queries on large datasets.
⚠ Common exam trap
A common mix-up: candidates choose 'Increase the database server's RAM' because they think more memory will speed up all queries, but without an index the database still must read every row from disk or memory, and RAM alone cannot eliminate the need for a full table scan.
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
✓
Create an index on the 'last_name' column.
Creating an index on the 'last_name' column allows the database to locate rows matching filter conditions without scanning the entire table. This dramatically reduces I/O and CPU overhead for queries that filter by last_name, directly addressing the performance bottleneck without requiring any changes to application code.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Partition the table by row count.
Why it's wrong here
Partitioning organizes data into smaller segments but does not inherently accelerate searches on a specific column.
- ✗
Increase the database server's RAM.
Why it's wrong here
More RAM may improve caching but is not a targeted solution for column-based filtering; it is less effective than indexing.
- ✓
Create an index on the 'last_name' column.
Why this is correct
An index on the filtered column enables rapid row retrieval, significantly speeding up queries.
- ✗
Denormalize the table to reduce joins.
Why it's wrong here
Denormalization introduces data redundancy and does not directly speed up filtering on 'last_name'.
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Same concept, more angles
1 more way this is tested on FC0-U71
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A database administrator adds an index on the 'Email' column of a 'Users' table. What is a likely consequence?
medium- A.Reduced storage space
- B.Improved query performance for all queries
- ✓ C.Slower update operations on the table
- D.Faster inserts on the table
Why C: Adding an index on the 'Email' column improves the speed of SELECT queries that filter or sort by that column, but it introduces overhead on write operations. Every time a row is inserted, updated, or deleted, the database must also update the index structure (e.g., a B-tree). This additional work makes UPDATE operations slower, which is why option C is correct.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.