What does an index usually improve?
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MySQL quiz
Evaluate MySQL fundamentals across SQL, indexes, joins, transactions, and query performance.
Database · About 3 minutes
MySQL quiz questions and answers
Review all 5 questions at your own pace. Open each answer to see the correct response and a concise explanation of the concept.
Topics covered
- Queries
- Joins
- Indexes
- Transactions
- Normalization
What does an index usually improve?
Correct answer
Read query lookup speed
Indexes help MySQL find rows faster, though they add write and storage cost.
Which SQL clause filters grouped results?
Correct answer
HAVING
HAVING filters after GROUP BY aggregation, while WHERE filters rows before grouping.
What does an INNER JOIN return?
Correct answer
Rows with matching values in both tables
INNER JOIN returns records that satisfy the join condition in both tables.
What is a transaction useful for?
Correct answer
Keeping multiple database operations atomic
Transactions ensure related changes either all commit or all roll back.
Which command helps inspect how MySQL will run a query?
Correct answer
EXPLAIN
EXPLAIN shows the query plan, including indexes and join strategy.
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