Test your SQL across filtering and NULL semantics, joins, aggregation, and window functions and constraints. 30 scenario questions, instant score by category, free with no signup.
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It spans beginner through expert in one sitting. The early questions cover things every SQL user meets — NULL comparisons, INNER vs LEFT JOIN, BETWEEN's boundaries. The later ones go into join fan-out with aggregates, window functions, CTEs, transaction isolation and constraints. Your score places you in one of four tiers, and the tier names are deliberately the ones job postings use.
No. Every question is written against standard SQL behaviour shared across PostgreSQL, MySQL, SQL Server and SQLite — NULL semantics, join types, and the ANSI window function syntax. Nothing here depends on a vendor-specific extension.
It samples the same kind of read-and-predict reasoning most employer screens open with, in the same short-scenario format, which is why it works as preparation. It is not a copy of any specific employer test, and a good score here is not a certificate. What it does tell you is which of the four areas you would lose marks in, which is the useful thing to know before a technical interview.
About six minutes. There is no timer on individual questions — the test measures whether you know what the query returns, not how fast you can click. You can think about a question for as long as you like.
Taking our test should not be viewed as a comprehensive or precise evaluation of your abilities. Results are for informational and self-reflection purposes only.
Test your SQL across filtering and NULL semantics, joins, aggregation, and window functions and constraints. 30 scenario questions, instant score by category, free with no signup.
This is a scenario-based SQL test: 30 short queries, each followed by a question about what actually happens when it runs. A WHERE clause compared against NULL that quietly returns nothing. A LEFT JOIN that behaves like an INNER JOIN once you filter the wrong column. A NOT IN that silently drops every row because one value in the subquery was NULL. You pick the answer that matches what the database actually returns, not what looks like it should happen.
The 30 questions cover four areas — filtering and NULL semantics, joins and set operations, aggregation and subqueries, and window functions/CTEs/transactions/constraints. Those four are the places where reading a query and running a query quietly diverge, and where a job posting's Strong SQL usually turns out to mean something specific once you are in the interview. You get a score in each area, so a weak spot shows up as a weak spot rather than as a lower total.
It takes about six minutes, there is no signup, and there is no query to write or execute — every question is read-and-predict, the same way a senior engineer reviews a pull request. Knowing the syntax and knowing what a specific query does against specific data are different skills, and this measures the second one.
See which of the four SQL areas is actually holding you back
Get a breakdown by category — filtering/NULLs, joins, aggregation, windows/transactions
Find out which tier you are in: beginner, intermediate, advanced or expert
Compare where you sit against what job postings mean by strong SQL
A table has a nullable column age. You run SELECT * FROM users WHERE age = NULL. How many rows does this return, even if several rows have age set to NULL?
30 questions, 6 min. Auto-advance — no manual Next.
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Test your SQL across filtering and NULL semantics, joins, aggregation, and window functions and constraints. 30 scenario questions, instant score by category, free with no signup.
No signup needed — your result appears instantly.
It spans beginner through expert in one sitting. The early questions cover things every SQL user meets — NULL comparisons, INNER vs LEFT JOIN, BETWEEN's boundaries. The later ones go into join fan-out with aggregates, window functions, CTEs, transaction isolation and constraints. Your score places you in one of four tiers, and the tier names are deliberately the ones job postings use.
No. Every question is written against standard SQL behaviour shared across PostgreSQL, MySQL, SQL Server and SQLite — NULL semantics, join types, and the ANSI window function syntax. Nothing here depends on a vendor-specific extension.
It samples the same kind of read-and-predict reasoning most employer screens open with, in the same short-scenario format, which is why it works as preparation. It is not a copy of any specific employer test, and a good score here is not a certificate. What it does tell you is which of the four areas you would lose marks in, which is the useful thing to know before a technical interview.
About six minutes. There is no timer on individual questions — the test measures whether you know what the query returns, not how fast you can click. You can think about a question for as long as you like.
