Indexing basics: B-trees and hash

What you’ll practice

Expect practical, scenario-based questions on how B-tree and hash indexes behave under different workloads and query shapes.

You’ll reinforce core ideas like key ordering, lookup paths, selectivity, and why an index can help one query while barely affecting another.

Quiz format and difficulty

Each question comes with 4 options and there’s no timer, so you can reason through execution details without rushing.

Pick the question count you want before starting, and choose a difficulty setting to focus on fundamentals, challenge yourself, or mix both for balanced coverage.

Common pitfalls to watch for

Many mistakes come from assuming “an index always helps” or mixing up what ordering enables (range scans) versus what hashing optimizes (exact matches).

Another frequent trap is ignoring maintenance cost: inserts/updates, page splits, and how index choice affects write-heavy tables.

• Confusing point lookups with range queries when choosing B-tree vs hash
• Overestimating index benefits on low-selectivity columns
• Forgetting that extra indexes speed reads but can slow writes
• Mixing up clustered vs non-clustered behavior and what it implies for I/O
• Misreading composite index rules (leftmost prefix and column order)

How the difficulty stays balanced

Easy items check definitions and basic behaviors, while harder ones ask you to infer the best index for a query pattern or predict performance trade-offs.

Mixed difficulty keeps the quiz approachable while still preparing you for real database tuning decisions.