// Phase 1 · Interview-ready languages · course 2
Databases & SQL
Almost every app stores data. Learn to query it with SQL, a skill that shows up in nearly every junior job description.
BeginnerFree course10 lessons ready3 coming soon
You'll be able to
- Understand tables, rows, columns and keys
- Filter and sort data with SELECT, WHERE and ORDER BY
- Combine tables with JOIN and summarize with GROUP BY
- Answer real business questions with a query
Syllabus
Start course →- 1Tables & SELECT QueriesRead data with SELECT, filter it with WHERE and sort it with ORDER BY.12 min
- 2Filtering Rows with WHEREAND, OR, IN, BETWEEN, LIKE and NULL. Ask exactly the question you mean.9 min
- 3Sorting, Limiting & DISTINCTOrder results, take the top N, and remove duplicates.7 min
- 4Counting & Summarizing (Aggregates)COUNT, SUM, AVG, MIN and MAX turn many rows into one answer.8 min
- 5Grouping Results with GROUP BYOne summary row per category, the query behind every dashboard.9 min
- 6Combining Tables with JOINSee exactly how INNER and LEFT JOIN match rows, then write your own.10 min
- 7JOINs & GROUP BYCombine tables and summarize data, the queries interviewers ask most often.15 min
- 8INSERT, UPDATE & DELETEAdd, change and remove data safely, and why WHERE is your seatbelt.9 min
- 9Designing & Creating TablesPick columns, types and keys that keep your data correct.10 min
- 10Subqueries & CTEsUse the answer of one query inside another, and keep complex queries readable.9 min
- 11Indexes: why queries get slowComing soon
- 12Window functions (ROW_NUMBER, RANK)Coming soon
- 13Using a database from your codeComing soon