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§ cs 503 · 7 guides

CS 503 — SQL III — Systems

Indexes, query plans, transactions, isolation levels, normalization, partitioning, OLTP vs OLAP — running a database in production, not just querying one.

Level
7 guides
# Code Name Level Updated
1 —
EXPLAIN and Query Plans How the planner decides between sequential scan, index scan, nested loop, hash join, and merge join — and how to read the output without panicking.
intermediate
2 —
Indexes — B-tree, Hash, GIN, BRIN The data structures that turn O(n) table scans into O(log n) lookups — when each index type helps and when it actively hurts.
intermediate
3 —
Isolation Levels Read committed, repeatable read, snapshot, serializable — what each prevents, what each still lets through, and why your DB lies about which one you asked for.
advanced
4 —
Normalization — 1NF, 2NF, 3NF (and When Not To) Codd's normal forms eliminate redundancy in transactional schemas — and analytics deliberately denormalises them right back.
intermediate
5 —
OLTP vs OLAP — Row Stores vs Column Stores Why Postgres serves your app in milliseconds and Snowflake aggregates a billion rows in seconds — same SQL, fundamentally different storage.
intermediate
6 —
Partitioning and Sharding Split one big table into many small ones — by range, list, or hash — so the planner only touches what it has to.
advanced
7 —
Transactions and ACID BEGIN, COMMIT, ROLLBACK — and what atomicity, consistency, isolation, and durability actually buy you when concurrent writers fight.
intermediate