data · 23 lessons
SQL & PostgreSQL concepts
Relationships, integrity, queries, transactions, and concurrency.
What you are working toward
Query real local data and reason about production database boundaries.
0 learning steps complete · View prerequisites and evidence →
The existing foundation
Start here, or use it to fill a gap.
Original lessons, practice, bosses, and progress are preserved. Completion from this journey is distinct from the new independent evidence model.
- 01SELECTGuided foundationOpen →
- 02WHEREGuided foundationOpen →
- 03ORDER BY & LIMITGuided foundationOpen →
- 04DISTINCTGuided foundationOpen →
- 05AggregatesGuided foundationOpen →
- 06GROUP BYGuided foundationOpen →
- 07HAVINGGuided foundationOpen →
- 08JOINsGuided foundationOpen →
- 09INNER vs LEFT JOINGuided foundationOpen →
- 10CASEGuided foundationOpen →
- 11SubqueriesGuided foundationOpen →
- 12CTEsGuided foundationOpen →
- 13DatesGuided foundationOpen →
- 14Window functionsGuided foundationOpen →
- 15NULL handlingGuided foundationOpen →
Engineering sequence
Relational authority
Engineering sequence
Query reasoning
Engineering sequence
State under change
- 05Make a change an all-or-nothing unitintermediate · 22 min · predict, experiment, debug, buildunseen
- 06Reason about two writers, not one happy pathadvanced · 26 min · predict, experiment, debug, buildunseen
- 07Change a schema while old data still existsadvanced · 23 min · predict, experiment, debug, buildunseen
- 08Reconcile claims against evidenceproduction · 25 min · predict, experiment, debug, buildunseen