SQL Fundamentals — Query Any Database
The one language every developer needs. Learn SQL from simple selects to complex joins, subqueries, and aggregations. Practical patterns for real-world data questions. Works with PostgreSQL, MySQL, SQLite, SQL Server — core SQL is universal. Stop guessing at queries. Understand what you're asking the database to do.
Lessons
Lesson 1: SELECT Basics — Asking Questions
Master the fundamentals of SQL queries: SELECT, FROM, WHERE, filtering, pattern matching, NULL ha...
Lesson 2: Aggregations — Summarizing Data
Learn to summarize and analyze data using COUNT, SUM, AVG, MIN, MAX, GROUP BY, and HAVING. Master...
Lesson 3: JOINs — Combining Tables
Learn how to combine data from multiple tables using INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL ...
Lesson 4: Subqueries — Queries Inside Queries
Master nested queries, correlated subqueries, EXISTS, IN, and learn when to use subqueries versus...
Lesson 5: Data Modification — INSERT, UPDATE, DELETE
Learn to add, modify, and delete data safely. Master INSERT, UPDATE, DELETE statements with prope...
Lesson 6: Table Design — CREATE and ALTER
Design robust database tables with proper data types, constraints, and indexes. Learn to create, ...
Lesson 7: Advanced Queries — Window Functions
Master window functions for sophisticated data analysis: ROW_NUMBER, RANK, DENSE_RANK, running to...
Lesson 8: Performance & Best Practices
Master SQL optimization: reading EXPLAIN plans, index strategies, avoiding N+1 queries, and writi...