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Learn SQL

Go from your first SELECT to reliable multi-table reports. Learn joins and deliberate writes, then deepen your toolkit with CTEs, window functions, existence tests, combined results, and transactions.

20 lessons6 modules3.7 hours of practice4 challenges
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No installation. Your code runs right in the browser. No SQL experience needed. All sample tables are provided.

What you will be able to do

Course outline

Module 1

Read & shape results

Choose columns, remove duplicates, and filter records.

  1. Meet your first databaseSELECT your data · 5 min
  2. Choose useful columnsDISTINCT, expressions & aliases · 8 min
  3. Find what mattersFiltering with WHERE · 6 min
Module 2

Ask precise questions

Combine conditions, sort results, and calculate labels.

  1. Ask a more specific questionCombining conditions · 7 min
  2. Bring a little orderORDER BY & LIMIT · 6 min
  3. Turn values into labelsCASE expressions · 8 min
Module 3

See patterns in data

Aggregate, filter groups, and compare with a subquery.

  1. See the bigger pictureAggregates & groups · 7 min
  2. Filter a group, not a rowHAVING & aggregate conditions · 9 min
  3. Ask a question inside a questionSubqueries · 9 min
Module 4

Relationships & real reports

Join tables, modify records, and report on every course.

  1. Connect related tablesINNER JOIN & keys · 11 min
  2. Change data deliberatelyINSERT, UPDATE & DELETE · 11 min
  3. Project: a course activity reportFinal project · joins & aggregates · 20 min
Module 5

Explain a more complex report

Handle missing averages, name query stages, rank rows, and retain detail alongside totals.

  1. Calculate an average without inventing dataNULLIF, numeric division & ROUND · 12 min
  2. Name each stage of a queryCommon table expressions · 13 min
  3. Number rows without grouping them awayROW_NUMBER & window ordering · 13 min
  4. Show detail alongside its group totalPARTITION BY & window aggregates · 13 min
Module 6

Trustworthy database features

Test relationships, combine results, use transactions, and build a ranked learner report.

  1. Ask whether a relationship existsEXISTS & NOT EXISTS · 12 min
  2. Combine compatible result setsUNION ALL & provenance · 12 min
  3. Treat related changes as a transactionBEGIN, COMMIT & ROLLBACK · 15 min
  4. Project: a ranked learner activity reportCapstone · CTEs, joins & dense ranks · 25 min

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Every lesson is short, hands-on, and checked automatically.

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