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MySQL Practice Online with Queries and Exercises

MySQL practice online lets you write and run queries without installing a local database server. SQL Arena provides a dedicated MySQL sandbox for practicing queries, exercises, and MySQL-specific functions directly in the browser.

Updated · SQL Arena team

SQL on MySQL trackAll problems

What you will practice

  • Write and run queries on MySQL 8
  • Combine grouped values with GROUP_CONCAT
  • Handle missing values with IFNULL
  • Format dates with DATE_FORMAT
  • Understand MySQL-specific JOIN, LIMIT, and identifier syntax

A practice problem in the trainer

This is how a problem looks in SQL Arena: the task, the editor, the result and the database schema.

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TaskSubmissionsAI Mentor
List confirmed attendees for every workshop

You have workshops and their registrations. Return every workshop title as workshop and its confirmed attendee names as confirmed_attendees, alphabetically ordered and separated by commas. Return none when a workshop has no confirmed attendees. Sort the rows by workshop id.

Query 1MySQLv8.0
SELECT w.title AS workshop,
       IFNULL(GROUP_CONCAT(r.attendee_name ORDER BY r.attendee_name SEPARATOR ', '), 'none') AS confirmed_attendees
FROM workshops w
LEFT JOIN registrations r
  ON r.workshop_id = w.id AND r.status = 'confirmed'
GROUP BY w.id, w.title
ORDER BY w.id;
Submit
Resultworkshopsregistrations
Answer accepted

MySQL Practice Query with GROUP_CONCAT and LEFT JOIN

The result must keep every workshop, including workshops without confirmed registrations. That makes workshops the left side of a LEFT JOIN. The condition r.status = 'confirmed' belongs in the ON clause so only confirmed registrations are attached while unmatched workshops remain in the result.

Once the rows are grouped by workshop, GROUP_CONCAT turns several attendee names into one value. MySQL lets us put ORDER BY inside GROUP_CONCAT, so names within each workshop are assembled alphabetically. SEPARATOR ', ' controls exactly how the individual names are joined.

Poster Design only has a cancelled registration, while Indoor Garden has no registrations at all. In both cases, there is no confirmed name after the join. GROUP_CONCAT therefore returns NULL, and IFNULL converts that value to the requested text none.

Moving the status condition to WHERE would produce a different result. Rows with no matching registration have NULL values on the right side, and WHERE r.status = 'confirmed' would remove them. This is a common source of bugs in LEFT JOIN exercises because a filter can accidentally turn the intended outer join into behavior much closer to an inner join.

There are two separate ordering requirements in this query. ORDER BY inside GROUP_CONCAT controls the order of names within one aggregated string. The final ORDER BY w.id controls the order of the result rows themselves. One does not replace the other.

An online SQL compiler for MySQL is useful for testing syntax and running queries without configuring a local server. For meaningful practice, go beyond isolated SELECT statements and work with joins, grouping, subqueries, aggregation, and MySQL-specific functions. GROUP_CONCAT can combine multiple group values into one string, IFNULL can replace NULL with another value, and DATE_FORMAT formats date values. Practicing these features on MySQL itself matters because functions and syntax vary between SQL dialects.

SQLMySQL v8.0
SELECT w.title AS workshop,
       IFNULL(GROUP_CONCAT(r.attendee_name ORDER BY r.attendee_name SEPARATOR ', '), 'none') AS confirmed_attendees
FROM workshops w
LEFT JOIN registrations r
  ON r.workshop_id = w.id AND r.status = 'confirmed'
GROUP BY w.id, w.title
ORDER BY w.id;
Query result
workshopconfirmed_attendees
Ceramics LabAnna, Mila
Street PhotoLeo
Bread BasicsDaniel, Oliver, Sofia
Poster Designnone
Indoor Gardennone

Common MySQL Practice Query Mistakes

01

Filtering the right table in WHERE

A LEFT JOIN can preserve unmatched rows, but a later WHERE condition on the right table can remove them again because those columns contain NULL. When every row from the left table must remain, check whether the right-side condition belongs in ON instead.

02

Trying to use FULL OUTER JOIN

MySQL does not provide a standard FULL OUTER JOIN operator. Exercises that need unmatched rows from both sides require another approach, so copying a query written for a different database may fail even when the relational idea is correct.

03

Using functions from another SQL dialect

MySQL has its own familiar toolkit, including IFNULL, GROUP_CONCAT, and DATE_FORMAT. Other engines often use different names or syntax for the same goal. Practicing against MySQL itself is the easiest way to notice those differences.

Practice problems on this topic

SQL on MySQL track

After this GROUP_CONCAT example, try MySQL exercises that change both the schema and the question. Beginner tasks include selecting five-star hotels, counting spacious rooms, finding platinum-tier loyalty members, and counting long-haul flights. More advanced exercises introduce multi-table aggregation and absence checks, such as finding guests with multiple bookings, calculating miles earned per member, or identifying members who never redeemed miles. SQL Arena runs these queries in a dedicated MySQL 8 sandbox rather than translating them to another engine. Across the platform there are 1,192 exercises, with each exercise using its own tables. Automatic checking also tests the query on hidden data, which helps catch solutions that only happen to match the visible sample. The free tier includes 292 exercises across PostgreSQL, MySQL, ClickHouse, and BigQuery without requiring a card. For a more directed route, continue with the SQL on MySQL developer track. ER diagrams can help when a schema has several relationships, EXPLAIN is available for inspecting query execution, and the AI mentor can provide hints or explain an error when you get stuck.

Reference on this topic

In-depth articles with syntax and examples in the SQL Arena reference.

Frequently asked questions

Where can I practice MySQL online?

Use a browser environment that runs queries on MySQL rather than a generic SQL interpreter. SQL Arena provides a dedicated MySQL sandbox for writing and checking queries online.

What is the best way to practice MySQL queries?

Practice by writing complete queries against tables rather than only reading syntax examples. Cover filtering, joins, grouping, subqueries, aggregation, and MySQL-specific functions.

What MySQL queries should I practice?

Start with SELECT, WHERE, ORDER BY, JOIN, GROUP BY, and aggregate functions. Then practice subqueries and MySQL-specific features such as GROUP_CONCAT, IFNULL, and DATE_FORMAT.

What is an online SQL compiler for MySQL?

It is a browser-based editor that sends SQL to a MySQL environment and returns the result. It allows you to test MySQL queries without installing and configuring MySQL locally.

Can I practice MySQL without installing it?

Yes. A browser-based MySQL sandbox can execute queries remotely, so no local database installation is required.

See also

Practice MySQL Queries Online

Open the MySQL 8 sandbox and start with free Easy tasks. There is no database setup or card requirement.

Practice MySQL

More practice from CodeRang