Database Systems — ZeroCourse

reading · we frame, you read MIT or the canonical taught · we author, no canonical fits ↺ spirals back to earlier lessons

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Complete Transport and Network Layer first.

This course unlocks once you've finished its prerequisite. Open prerequisite →

Prerequisites

Trees and Priority Queues not yet

Hashing and Advanced Linear Structures not yet

Network Fundamentals and Application Layer not yet

Complete prerequisites first to enroll.

reading · 30 min + ~221 min canonical

The Relational Model, SQL, and Normalization

You have written thousands of database queries, and you have probably never stopped to notice that the entire relational model rests on a single, beautiful mathematical idea: a ta…

primary CMU 15-445 Database Systems by Andy Pavlo (YouTube)

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reading · 35 min + ~221 min canonical L1

Indexing and How Queries Run: B-Trees, Plans, and EXPLAIN

You have added indexes to speed up slow queries, and you have watched an index mysteriously not get used and had no idea why. This lesson ends the mystery. An index is a data stru…

primary CMU 15-445 Database Systems by Andy Pavlo (YouTube)

after L1 locked

reading · 35 min + ~221 min canonical L1

Transactions, ACID, and Concurrency Control

Two customers hit "buy" on the last item in stock at the same instant. Two API requests both read a balance of $100, both subtract $30, both write $70 — and $30 vanishes into thin…

primary CMU 15-445 Database Systems by Andy Pavlo (YouTube)

after L2 locked

reading · 35 min + ~221 min canonical L1

Storage Internals and Recovery: B-Trees, LSM-Trees, WAL, and VACUUM

Beneath the SQL, the indexes, and the transactions is the layer where a database meets the disk — and this is where a lot of "why is PostgreSQL doing that?" mysteries get their an…

primary CMU 15-445 Database Systems by Andy Pavlo (YouTube)

after L3 locked

reading · 35 min + ~221 min canonical L1

Distributed Data and the ActiveRecord Lens: NoSQL, CAP, Replication, and the ORM

This lesson closes the database course by answering two questions. First: what happens when one machine can no longer hold or serve all your data? You replicate it (copies for ava…

primary CMU 15-445 Database Systems by Andy Pavlo (YouTube)

after L4 locked

exercise reading · 15 min L1

Exercises: Easy (Warm-up)

- [ ] SQL: Write queries to find duplicate rows in a table — GROUP BY ... HAVING COUNT() > 1 - [ ] SQL: Join 3 tables (users, orders, products) — Inner join, left join, aggregate …

after L5 locked

exercise reading · 30 min L1

Exercises: Medium (Core)

- [ ] SQL: Monthly revenue report with year-over-year comparison — LAG() window function - [ ] SQL: Find the Nth highest salary without LIMIT — Correlated subquery approach - [ ] …

after L6 locked

exercise reading · 45 min L1

Exercises: Hard (Stretch)

- [ ] Implement a simple write-ahead log (WAL) in Ruby — Append operations to log, replay on crash recovery - [ ] Implement MVCC in Ruby — Version each row with transaction ID, im…

after L7 locked

exercise reading · 60 min L1

Mini-Project

- [ ] Build a key-value database in Ruby — B-Tree index, WAL for durability, page-based storage, support GET, PUT, DELETE, SCAN; persist to disk, recover from crash

after L8 locked

L10

project reading · 480 min L1

Project: B-Tree in Ruby

Implement a B-tree (order 4) with insert, search, delete, and range scan. Visualize the tree structure after each operation showing splits and merges. This is the core index struc…

after L9 locked

L11

project reading · 360 min L1

Project: SQL Query Planner

Build a simple SQL parser in Ruby that handles SELECT ... FROM ... WHERE ... ORDER BY ... LIMIT. Parse into an AST, then generate a query plan (sequential scan vs index scan based…

after L10 locked

L12

project reading · 600 min L1

Capstone: Mini Database Engine

- [ ] Milestone 1: Page-based storage — read/write fixed-size pages to a file - [ ] Milestone 2: B-tree index — insert, search, range scan on pages - [ ] Milestone 3: SQL parser —…

after L11 locked

L13

assessment reading · 70 min L1

Self-Assessment: Database Systems

- [ ] Explain normalization up to 3NF. What is denormalization and when would you use it? - [ ] What is a B-Tree index? Why are B-Trees preferred over BSTs for database indexes? -…

after L12 locked

13 lessons. Read in order; spiral back when you need to. By the end you'll have used the core ideas twice — once on the abstract, once on something you'll meet at work next week.