SQL · Interactive Curriculum
Learn SQL Online
From Queries to Optimization
A free interactive SQL course with a live query playground for SELECT, JOIN, GROUP BY, subqueries, window functions, indexes, and query optimization.
1SELECT 'Hello, SQL!' AS message;Why Learn SQL?
Discover the benefits of learning SQL for data management.
Career Essential
SQL skills are required for data engineering, analytics, and backend development.
All SQL Lessons
Browse the complete ordered curriculum. Each lesson has a readable page you can link to and share.
Introduction to SQL
Learn the basics of SQL and how to interact with databases using queries
Selecting Data
Master the SQL SELECT statement to retrieve specific data from your database. Learn column aliases, DISTINCT, LIMIT, and expressions.
Filtering and Sorting
Learn SQL WHERE clauses and ORDER BY to filter and sort query results. Covers IN, BETWEEN, IS NULL, and LIKE for precise data retrieval.
Inserting and Updating Data
Learn SQL INSERT, UPDATE, and DELETE statements to add, modify, and remove data in your database tables safely.
Joins and Relationships
Learn how to combine data from multiple tables using JOIN statements and understand table relationships
Aggregation and Grouping
Learn to summarize data with aggregate functions like COUNT, SUM, AVG, and GROUP BY
Subqueries
Learn to write queries within queries using scalar subqueries, correlated subqueries, EXISTS, and IN
Indexes and Performance
Learn how SQL indexes speed up queries. Create indexes, analyze query plans with EXPLAIN, and optimize database performance.
Views and CTEs
Learn to organize complex queries with views, Common Table Expressions, and recursive CTEs
Transactions
Learn how to use transactions to ensure data consistency with BEGIN, COMMIT, ROLLBACK, and SAVEPOINT
Triggers and Automation
Learn SQL triggers to automate database actions. Create audit trails, enforce rules, and run logic on INSERT, UPDATE, and DELETE events.
Window Functions
Learn to perform advanced calculations with ROW_NUMBER, RANK, PARTITION BY, LAG, LEAD, and running totals
Database Design
Learn database design with normalization, entity-relationship modeling, primary and foreign keys, and constraints for clean schemas.
Migrations
Learn to evolve your database schema safely with ALTER TABLE, data migrations, and strategies for backward-compatible changes.
Capstone Project
Build a complete e-commerce database with SQL. Design schemas, write complex joins, aggregations, window functions, and analytics queries.
String Functions
Master SQL string functions to clean, transform, and extract text data. Learn UPPER, LOWER, SUBSTRING, REPLACE, and TRIM.
Date and Time Functions
Master SQL date and time functions to query, format, and calculate temporal data. Extract date parts, compute intervals, and filter by ranges.
Null Handling
Understand how NULL works in SQL. Learn COALESCE, NULLIF, and IS NULL to write queries that handle missing data correctly.
Set Operations
Learn SQL set operations to combine and compare result sets. Master UNION, INTERSECT, and EXCEPT for multi-query analysis.
Data Types And Casting
Understand SQL data types and type casting. Learn implicit and explicit conversion with CAST to avoid errors and data loss.
Constraints And Keys
Learn SQL constraints to enforce data integrity. Cover PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, CHECK, and DEFAULT values.
Recursive Queries
Learn recursive SQL queries with WITH RECURSIVE CTEs to traverse hierarchical data, generate sequences, and solve self-referencing problems.
JSON in SQL
Learn to store and query JSON data in SQL. Use JSON functions, path expressions, and table-valued functions for semi-structured data.
Triggers and Events
Go beyond basic SQL triggers: WHEN filters, RAISE resolutions, UPDATE OF column lists, INSTEAD OF triggers on views, and recursive triggers.
Query Optimization
Learn SQL query optimization with execution plans, index strategies, and common performance pitfalls to make your queries faster.
Frequently Asked Questions
- Can I learn SQL here for free?
- Yes. LearningSQL.org is free, and the lessons come with a live query playground so you can practice SELECT, JOIN, aggregation, indexes, window functions, and query optimization as you go.
- Can I practice without installing a database?
- You can. Queries run in the browser against a sandboxed database, so there is nothing to install first, no PostgreSQL, MySQL, or SQLite needed to get started.
- Is this a good place to start from scratch?
- It is. You begin with SELECT statements and filtering, then work your way up through joins, grouping, subqueries, indexes, transactions, window functions, and optimization.
- What is the best way to practice SQL?
- Write real queries against the sample tables and actually look at what comes back. Then change one thing at a time, the WHERE, the JOIN, the GROUP BY, the ORDER BY, and watch how each clause reshapes the result. That is how it sticks.