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🗃️ SQL Deep Dive

GROUP BY, subqueries, transactions — real SQL in your browser.

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