Databases and SQL: Your First 8 Queries

⚠️ Version note. SQL is remarkably stable — these eight queries work across SQLite, PostgreSQL, MySQL and most databases with tiny differences. Tool interfaces vary. Last checked: 25 July 2026.

What you'll have at the end

• A mental model of a database vs a spreadsheet, and what SQL is for
• Eight queries you wrote and ran, from SELECT to JOIN
• The ability to answer real questions by asking the data directly

Prerequisite

• TC-01 — What a Computer Actually Does is enough. No prior coding required — SQL reads almost like English.
• A place to run SQL: a browser-based SQL sandbox, or SQLite locally.

Why SQL, when you have spreadsheets?

A spreadsheet is fine for a few thousand rows you eyeball. A database holds millions, keeps them structured, and lets many programs use them at once. SQL (Structured Query Language) is how you ask it questions — and it's one of the highest-leverage, longest-lived skills in tech: the same language runs analytics, apps and dashboards, and it's barely changed in decades.

The mental shift: instead of scrolling and filtering by hand, you describe what you want and the database fetches it. Eight patterns cover most of it.