Guided Notes

Introduction to SQL

Databases, tables and schemas, plus SELECT, filtering, and aggregation basics.

What is SQL?

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SQL (Structured Query Language) is how you ask a relational database for data. Nearly every company stores its customers, orders, and transactions in databases, and SQL is the common language for reading them β€” in MySQL, PostgreSQL, SQL Server, SQLite, and cloud warehouses like Google BigQuery.

A query describes the result you want, not the steps to get it. The database works out how to find the rows efficiently.