What is table partitioning and when should you use it?

Partitioning divides a large table into smaller physical sub-tables (partitions) while presenting them as a single table to queries. Types: Range (most common): partition by date, number range. List: partition by discrete values (country, region). Hash: even distribution. When to use: 1) Table > ~100GB AND queries commonly filter by the partition key. 2) Archival: easily drop old partitions (vs sl