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FC0-U71 Practice Question: A database administrator adds an index on the…
A database administrator adds an index on the 'Email' column of a 'Users' table. What is a likely consequence?
⚠ Common exam trap
Watch out — candidates often assume indexes universally speed up all database operations, ignoring the write-performance penalty that occurs because the index must be maintained on every INSERT, UPDATE, and DELETE.
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
✓
Slower update operations on the table
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Reduced storage space
Why it's wrong here
Indexes consume additional disk space.
- ✗
Improved query performance for all queries
Why it's wrong here
Only queries that use the indexed column benefit.
- ✓
Slower update operations on the table
Why this is correct
Index maintenance adds overhead to INSERT/UPDATE/DELETE.
- ✗
Faster inserts on the table
Why it's wrong here
Inserts become slower due to index update.
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