Introduction

A database is a collection of data that can be searched and retrieved. A database management system (DBMS) is a program that manages a particular kind of database. Each DBMS stores data in its own way: SQLite stores each database in a single file, while PostgreSQL spreads information across many files for higher performance. A DBMS can be a library embedded in other programs (like SQLite) or a server (like PostgreSQL).

A relational database management system (RDBMS) stores data in tables and uses SQL for queries. Unfortunately, every RDBMS has its own dialect of SQL. There are also NoSQL databases like MongoDB that don't use tables, but we won't cover them here.

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