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Beginner30 questions30 minutes

SQL Beginner Quiz

SELECT, WHERE, JOIN and GROUP BY — the everyday clauses, checked by reading real queries.

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Sample questions from this quiz

A preview of the style and depth. Try each one, then reveal the answer — or skip straight to the timed quiz.

1. The users table has 10 rows. What does this return?

SELECT COUNT(*) FROM users;
  • 10 rows
  • One row containing 10
  • One row containing 1
  • An error — COUNT needs a column
Show answer

Answer: One row containing 10. An aggregate with no GROUP BY collapses the whole table into a single row. `COUNT(*)` counts rows; `COUNT(column)` counts only rows where that column is not NULL, which is a distinction worth internalising early.

2. What does this return?

SELECT name FROM users WHERE age > 18 ORDER BY name;
  • Names of users older than 18, sorted alphabetically
  • All names, sorted by age
  • Names of users aged 18 or older
  • The single oldest user's name
Show answer

Answer: Names of users older than 18, sorted alphabetically. WHERE filters rows before they are returned, and ORDER BY sorts the result. Note `> 18` excludes exactly 18 — use `>=` to include it. Sorting is ascending by default; add DESC to reverse it.

3. Fill in the blank to keep only distinct values.

SELECT ____ country FROM users;
  • DISTINCT
  • UNIQUE
  • ONLY
  • SINGLE
Show answer

Answer: DISTINCT. DISTINCT removes duplicate rows from the result. UNIQUE exists in SQL but as a table constraint, not a SELECT modifier. With several columns, DISTINCT deduplicates the whole combination rather than each column separately.

Frequently asked questions

How many questions are in this SQL quiz?+

30 questions, with a 30-minute time limit. Every question includes a written explanation of the correct answer.

Is this SQL quiz free?+

Yes. Every quiz on CodexQuizz is free and needs no account. You only enter a name if you choose to post your score to the leaderboard.

What level is the beginner quiz aimed at?+

SELECT, WHERE, JOIN and GROUP BY — the everyday clauses, checked by reading real queries.

Can I use this to prepare for a SQL interview?+

Yes. The questions cover the topics that come up in SQL technical screens, and the explanations are written so that a wrong answer still teaches you the underlying concept.

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