7 lessons
Storage devices and file basics
The memory hierarchy from registers to disk, how a database file is organized into blocks and records, and the math behind why disk access dominates database performance.
RAID: combining disks for speed and safety
How RAID levels 0, 1, 5, and 10 trade off performance, storage efficiency, and fault tolerance by spreading and duplicating data across multiple physical disks.
File organization: heap, sequential, and hashing
The three fundamental ways to physically arrange records in a file, and the worked disk-access math comparing insertion, search, and deletion cost for each.
Indexing fundamentals: dense, sparse, and multilevel indexes
What an index actually is — a small lookup table pointing at the real data — and how dense, sparse, and multilevel indexes trade index size against search speed.
B-tree indexing
The self-balancing multi-way search tree that keeps every lookup, insertion, and deletion within a guaranteed, small number of disk accesses, no matter how much the data grows.
B+ tree indexing
How the B+ tree differs structurally from the B-tree, why every leaf-linked-list detail exists, and why it's the dominant index structure in production databases.
Hashing techniques: static and dynamic
Static hashing's fixed-bucket weakness, and how extendible and linear hashing solve it by growing incrementally as data grows.