Relational Fundamentals
The model, the query, and the two mechanisms — indexes and the planner — that decide whether it returns in 2ms or 2s.
6 topics
Relational Model & Normalisation
Why the relational model stores each fact once, and when deliberately breaking that rule is the right call.
core25 minSQL That Earns Its Keep
The handful of SQL features — aggregation, window functions, CTEs, upserts — that replace a loop in application code.
core30 minJoins & Join Algorithms
What each join type returns, and the three physical algorithms the planner picks between to produce it.
core25 minIndexes & How They Work
A B-tree index is a sorted structure the database can binary-search, and every rule about column order and selectivity follows from that.
core30 minReading a Query Plan
How to run EXPLAIN ANALYZE and find the one node where the estimate and the reality diverge.
core25 minConstraints & Data Integrity
Why the invariant belongs in the schema rather than in application code, and what each constraint type actually guarantees.
core20 min