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20 QUESTIONS · 5 TOPICS · NORMALISATION WALKTHROUGH · ABOUT 12 MINUTES

Store each fact once. Then everything else follows.

Databases keep banks, airlines and every app you use consistent, even when thousands of people write at once. Twenty questions on how, each explained, then untangle a messy table yourself. No sign-up, nothing saved.

Start the test
AAtomicityAll of a transaction happens, or none of it.
CConsistencyEvery change leaves the rules intact.
IIsolationConcurrent transactions don't see each other's half-done work.
DDurabilityOnce committed, it survives a crash.
QUESTION 1 / 20 · RELATIONAL MODELEasy

In a relational database, what uniquely identifies each row in a table?

NORMALISATION, STEP BY STEP

From one messy table to clean ones

Orders
OrderIDCustomerCityProducts
101AshaLeedsPen £2, Pad £3102BenYorkPen £2103AshaLeedsInk £5
UnnormalisedOne table, one row per order, with a list of products squeezed into a single cell (shown in red).
PROBLEMYou can't easily query 'all orders containing Pen', and the cell format is up to whoever typed it.
Highlighted cells are repeated facts: each repeat is a place where an update could be missed.

What this database systems test covers, in short

Twenty multiple-choice questions at introductory undergraduate level, four on each of five topics: the relational model, SQL, normalisation, transactions and concurrency, and indexing and storage. They test how relational databases organise data and keep it correct.

SQL examples use standard syntax that works in PostgreSQL, MySQL and SQLite. The test is our own and not normed.

By What's Your IQ · Reviewed 5 Oct 2026
Format
20 multiple-choice questions
Level
Introductory undergraduate
Bonus
Unnormalised → 3NF walkthrough
Founding paper
Codd (1970), the relational model

Keep going

SQL testPredict the output of real queries on two small tables.Data structures testB-trees and hash tables power database indexes.Operating systems testConcurrency and locking from the OS side.

Clean structure, clear thinking. Test your reasoning.

Our full IQ test covers logical, numerical, verbal and spatial reasoning: 60 questions, about 30 minutes.

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