THE FORSK PRACTICE ROOM
SQL practice, one query at a time
Five original SQL lessons with one downloadable dataset, expected results and guided exercises.
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5 lessons to work through
5 lessons
SQL SELECT, WHERE and ORDER BY with a runnable dataset
Query a small student table, combine conditions and make the final row order deterministic.
SQL GROUP BY and HAVING: count learners by city
Aggregate rows into groups, filter groups with HAVING and avoid ambiguous ungrouped columns.
SQL INNER JOIN and LEFT JOIN: include learners with no enrolments
Join related tables and preserve unmatched students without accidentally counting a missing enrolment as a real one.
SQL NULL, COUNT and COALESCE: handle missing information
Distinguish a missing value from an empty string or zero, and interpret counts correctly.
SQL keys and constraints: reject invalid practice submissions
Define a small related table and understand which rules belong in database constraints.
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Build a learning habit that leaves evidence.
Save your working code, write down the mistake you corrected, and return to the exercise a day later. For guided classroom or online learning, explore the related Forsk courses.
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