SQL

Est. read time: 1 minute | Last updated: January 03, 2026 by John Gentile

Contents

SQL Language
References

SQL Language

SELECT name, population FROM world
  WHERE name IN ('Sweden', 'Norway', 'Denmark');

References

SQLZoo: tutorials to learn SQL step by step.
W3 Schools SQL Tutorial
SQLBolt: learn SQL with simple, interactive exercises.
PostgreSQL Exercises
PostgreSQL Tutorial - Learn PostgreSQL from Scratch
Use the Index, Luke!: a guide to database performance for developers.