SQL & Databases

The skill that pays off in every single engineering role.

beginner · 6–10 weeks · 3 milestones · 9 topics

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QueryingGet the data out, correctly.

Modelling & IntegrityA good schema prevents entire categories of bug.

PerformanceWhere SQL knowledge turns into real money saved.

Full outline

Query fluency, relational modelling, indexes and query plans, transactions, and the performance work that turns slow applications fast.

01Querying
Get the data out, correctly.
- The fundamentals
  Selection, filtering, sorting and aggregation.
- Joins
  Combining tables without accidentally multiplying rows.
- Window functions & CTEs
  The tier that separates casual SQL from professional SQL.
02Modelling & Integrity
A good schema prevents entire categories of bug.
- Schema design
  Model the domain, then let the database enforce it.
- Transactions
  Keeping data consistent when multiple writers collide.
- Migrations
  Changing a schema that already holds production data.
03Performance
Where SQL knowledge turns into real money saved.
- Indexes
  The single highest-leverage database skill.
- Query plans
  Stop guessing. Read what the planner actually does.
- Scaling
  What to do when one database stops being enough.