SQL: practice, test and prove it
A 10-question test on SELECT, joins, GROUP BY, NULL and keys.
FreeNo sign-up to testNo attempts yet
SQL questions are the same across data, backend and operations roles: filter, join, group, and avoid the traps around NULL and missing WHERE clauses. Every answer here explains the rule.
Benchmark: 80% pass mark; analyst and backend screenings expect joins and grouping. Requirements vary by employer.
Lessons
SELECT, WHERE and ORDER BYReading a table: choosing columns, filtering rows and sorting, with the mistakes that return wrong rows silently.Lesson 1
Joins and GROUP BYCombining two tables and summarising rows: the two topics every SQL interview asks about.Lesson 2
Subqueries, IN, EXISTS and the NULL trapsHow to nest one query inside another, and why NULL silently empties results in comparisons, NOT IN and counts.Lesson 3
Primary keys, foreign keys and changing data safelyWhat keys and constraints guarantee, how INSERT, UPDATE and DELETE work, and the WHERE-clause habit that prevents wiping a table.Lesson 4
Advertisement
Interview prep
SQL interview questionsThe standard SQL questions for data, analyst and backend roles, with short answers and the rule behind each.6 questions
SQL query-writing questionsQuestions where you write the query aloud or on a whiteboard, with model answers.6 questions
Certificate
Free with an accountA PDF with your name, best score and date. Records this site's tests only.
Common questions
Which database does the test assume?
Standard SQL. Where syntax differs (LIMIT versus TOP, date functions), the explanation says so.
Do I need to know window functions?
Not for this test. They appear in some analyst interviews; the query-writing set mentions one.
Is this enough for a data analyst role?
It covers the SQL part of most screenings. Analyst roles also test Excel and sometimes a BI tool.