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Learning resources

TeachyLeaf currently publishes free tutorials and browser-based tools. There are no paid courses available to enroll in.

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Published tutorials and tools

Start with a published lesson or try a browser-based utility.

SQL · Beginner

SQL SELECT and WHERE

Choose columns, filter rows, and inspect expected results using the shared sample dataset.

Read the SQL basics lesson

SQL · Beginner

SQL NULL handling

Use IS NULL and keep unmatched rows when filtering results from a LEFT JOIN.

Read the NULL lesson

Published tutorial

SQL INNER JOIN vs LEFT JOIN

Work through sample tables and compare the rows returned by each join.

Read the SQL lesson

SQL · Beginner

SQL GROUP BY and aggregates

Count orders, calculate totals, and filter grouped results with the shared sample data.

Read the aggregation lesson

SQL · Beginner

SQL constraints

Protect sample customer and order data with keys, required values, and validation rules.

Read the constraints lesson

SQL · Beginner

SQL transactions

Learn how to commit related changes or roll them back before committing.

Read the transactions lesson

SQL · Beginner

SQL indexes

Create an index for a common lookup and learn how query plans and index trade-offs work.

Read the indexes lesson

SQL · Database differences

MySQL and PostgreSQL CONCAT

Compare how CONCAT handles NULL and learn which behavior has been runtime-tested.

Read the SQL portability lesson

Laravel · Beginner

Laravel request lifecycle

Follow a real page request through its route, controller, and Blade view.

Read the Laravel lesson

Published guide

Common JSON syntax errors

See common JSON mistakes, corrected examples, and practical parser-debugging steps.

Read the JSON guide

Browser-based utilities

Developer tools

Use SQL, JSON, and URL component tools that explain their limits and how input is processed.

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