Database systems

Know exactly what your query is doing.

A full course, from an ER diagram on paper down to the B+ tree the database walks, the plan it picks, and the log it writes before it commits. The whole university syllabus, taught the way an engineer needs it.

Start with the introduction See all 34 chapters

Practise the SQL in a real database with ChaiCode SQL Labs

Handwritten A4: a bracket enclosing three operations, debit A, credit B, log entry, with BEGIN written at the top and COMMIT at the bottom. To the side, a second copy where a crash symbol interrupts the middle and an arrow labelled ROLLBACK returns everything to the start state.

Chapter 27, Transactions & ACIDWhat a transaction is

chapters

parts

239

illustrated pages

hours of reading

What the course covers

34 chapters in 7 parts.

Read them in order, or jump to the topic you need. Every section pairs a clear written explanation with a drawn page you can take in at a glance.

Databases notes: Why databases exist at all

Start hereIntroductionWhat this course covers, why databases are built the way they are, and how to read itWhy databases exist at allWhat this course coversHow to read these notesA word about SQL and NoSQLWhat you need before starting5 sections · 12 min

Part A

Foundations

Why databases exist, how a DBMS is built, data models, and ER design turned into tables.

5 chapters

Part B

The relational model and SQL

Relational algebra, DDL and DML, every kind of join, subqueries, aggregation and views.

7 chapters

Part C

Design and normalization

Functional dependencies, 1NF through BCNF and beyond, and when to stop normalizing.

4 chapters

Part D

Storage and indexing

Pages and heap files, B+ trees, hash indexes, composite and covering indexes, and why an index gets ignored.

6 chapters

Part E

Query processing and optimization

Physical operators, join algorithms, cost estimation, and reading a real EXPLAIN plan.

4 chapters

Part F

Transactions and recovery

ACID, schedules and serializability, locking, MVCC, isolation anomalies, and write-ahead logging.

5 chapters

Part G

Modern databases and capstone

Replication and sharding, SQL versus NoSQL, and designing a real schema end to end.

3 chapters

Questions

Good to know.

Who is this course for?

Students working through a university databases syllabus, and engineers who want to know why a query is slow, why an index was ignored, or what really happens between BEGIN and COMMIT. Everywhere the theory has a practical side, the course shows both.

How is a chapter laid out?

Each chapter opens with a short introduction, then works through its topic one section at a time. Every section pairs a drawn page with a written explanation, so you can take in the picture first and then read the detail. Some chapters (4 in all) also include an interactive figure you can step through.

How long does it take?

About 12 hours of reading in all, across 239 sections. A chapter takes between 18 and 24 minutes, so one fits comfortably into a study session.

Stop guessing what the database is doing.

Start with the introduction for a map of the whole course, then follow a query from the ER diagram all the way to the log.

Start with the introduction Browse the chapters