SQLExcelHTML & CSSPlay
Lurndo › Topics › SQL for your job interview

SQL for your job interview

Have a job interview with an SQL test coming up?

For jobs as a data analyst, controller, marketer or developer, employers ask for SQL more and more, and often there is a practical test in the interview. Reading theory won't help much then: you need to be able to write queries yourself, with a bit of pressure on.

With Lurndo you practise with real queries on real data, right in your browser. You see straight away what your query does, and when it's wrong you find out why.

Start free with the first lessonNo account needed · a lesson takes a few minutes

Why Lurndo suits you

  • Exactly what comes up in a test

    JOIN, GROUP BY and HAVING, subqueries, NULL and window functions such as ROW_NUMBER and RANK: the classics of an SQL test are all in the course.

  • Learn from your mistakes

    Every exercise explains why the answer is right. When you get it wrong, you see what went wrong, such as too many rows, a wrong column or a forgotten NULL.

  • Practise against the clock

    In the speedrun you answer quick questions with the timer running, just like in a real test. Every mistake costs ten seconds.

  • A cheat sheet for the night before

    All the SQL from the course on one page, to go through calmly before your interview.

Try a typical test question

Show the number of films per genre, but only for genres with at least 4 films.

Where should you start?

If you already know the basics, go for the topics that come up most in tests. Starting from zero? The first modules take you through it step by step.

  1. 4Fourth dayYour fourth client: De Trapper bike rental in Bruges. You learn to count, add up and average with COUNT, SUM, AVG, MIN and MAX, and to summarise everything per group with GROUP BY and HAVING.
  2. 5Fifth dayYour fifth client: football club FC De Kraaien in Lier. You learn to combine tables with keys and JOIN: INNER, LEFT, RIGHT and FULL, with aliases, across several tables and even a table with itself.
  3. 6Sixth dayYour sixth client: Het Leeslint library in Kortrijk. You learn to query smarter: reshaping text and dates, choosing with CASE, asking questions inside questions with subqueries and EXISTS, and keeping long queries readable with WITH.
  4. 8Eighth dayYour eighth client: the Ronde van het Pajottenland, a five-day stage race. You learn window functions: numbering with ROW_NUMBER, ranking with RANK, per group with PARTITION BY, standings with running totals, and combining lists with UNION.

Frequently asked questions

What SQL questions come up in a job interview?

Usually filtering data with WHERE, counting and grouping with GROUP BY and HAVING, combining tables with JOIN, and sometimes a subquery or a window function such as ROW_NUMBER. Pitfalls with NULL and duplicate rows come up a lot too.

How quickly can I prepare?

You can have the basics down in a few evenings. A lesson only takes a few minutes, so you can also practise in between. Short on time? Focus on the modules about counting, joins and subqueries.

Do I learn the SQL companies use?

You practise with SQLite, and the basics are the same in every database, whether it's MySQL, PostgreSQL or SQL Server. Where the dialects differ, the lessons say so.

Do I need to install anything?

No. Everything runs in your browser, on your phone too.

Ready for your test?

Start with the first lesson and see how far you get. The first three modules are free.

Start free with the first lesson
SQL topicsCheat sheetExcelLeaderboardAccountPrivacyNederlands