🗃️ SQL Deep Dive
GROUP BY, subqueries, transactions — real SQL in your browser.
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Lesson 1 — GROUP BY
medium · 9 min
Lesson 2 — HAVING
medium · 9 min
Lesson 3 — Indexes
medium · 8 min
Lesson 4 — UPDATE & DELETE
medium · 9 min
Lesson 5 — UNION
medium · 9 min
Lesson 6 — COALESCE (nulls)
medium · 9 min
Lesson 7 — GROUP_CONCAT
medium · 9 min
Lesson 8 — CASE labeling
medium · 9 min
Lesson 9 — NULL handling
medium · 9 min
Lesson 10 — Subqueries
hard · 11 min
Lesson 11 — Transactions
hard · 11 min
Lesson 12 — CTEs (WITH)
hard · 12 min
Lesson 13 — Transactions
hard · 12 min
Lesson 14 — CASE expressions
hard · 11 min
Lesson 15 — Self join
hard · 12 min
Lesson 16 — EXISTS
hard · 11 min
Lesson 17 — Row numbering
hard · 12 min
Lesson 18 — Mini project: report
hard · 13 min
Lesson 19 — Ranking with a subquery
hard · 12 min
Lesson 20 — Running total
hard · 12 min
Lesson 21 — Self join
hard · 12 min
Lesson 22 — Recursive hierarchy (expert)
hard · 13 min
Lesson 23 — Recursive hierarchy with depth
very hard · 16 min
Lesson 24 — EXISTS vs IN
very hard · 14 min
Lesson 25 — Ultimate: cohort report
★ ultimate · 20 min