Join
In plain terms
Combining rows from multiple tables based on related columns.
Going deeper
A SQL join merges data across tables using matching keys, letting you query related information together. It's fundamental to relational queries.
Under the hood
Join type and indexing drive performance; the planner picks nested-loop, hash, or merge joins.
Examples
SELECT ... JOIN, combining orders with customers, relational queries.
Think of it like...
Like matching a guest list to a seating chart by name to see who sits where.