🗄 Databases

Original CC BY-SA compilation from Wikipedia, licensed CC BY-SA 4.0.

From Codd's relational model through transactions, indexing, and NoSQL. Translated into runnable Scheme and Python with SVG diagrams.

	Chapter
1.	The Relational Model	Tables, rows, columns, and keys: Codd's foundation for all structured data	🗄
2.	Relational Algebra	Select, project, join, union, difference: the formal operations on relations	🗄
3.	SQL Basics	CREATE, SELECT, JOIN, GROUP BY: the language that implements relational algebra	🗄
4.	Normalization	Eliminate redundancy by decomposing tables according to functional dependencies	🗄
5.	Indexing	B-trees, B+ trees, and hash indexes: trade space for speed on lookups	🗄
6.	Transactions	ACID properties guarantee correctness when multiple operations must succeed or fail together	🗄
7.	Concurrency Control	Locks, two-phase locking, and MVCC: let multiple transactions run without corrupting data	🗄
8.	Recovery	Write-ahead logging and checkpoints: survive crashes without losing committed data	🗄
9.	Query Processing	Query plans, join algorithms, and cost estimation: how the engine picks the fastest path	🗄
10.	NoSQL and Beyond	Key-value, document, column-family, graph: when relations are not the right shape	🗄

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