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A free SQL tutorial in short lessons on one shop database. Every example runs on real PostgreSQL in your browser, and the page checks your answers.
DbSchema Blog
Database design, migrations, SQL and everyday database work — explained with practical examples.
SQL Aliases Explained with Examples | DbSchema
SQL aliases explained: rename columns and tables with AS, quote aliases with spaces or reserved words, and see where an alias may be referenced in WHERE, GROUP BY, HAVING and ORDER BY.
SQL WHERE Clause Explained with Operators and Examples | DbSchema
Learn how to use the SQL WHERE clause with comparison, range, list and pattern operators, NULL, AND/OR precedence, and UPDATE or DELETE, with every result shown.
SQL SELECT DISTINCT Statement Explained with Examples | DbSchema
SQL SELECT DISTINCT with single and multi-column examples, how NULL is handled, the ORDER BY error, COUNT(DISTINCT) on two columns, and DISTINCT vs GROUP BY.
MongoDB Relationships: Embed vs Reference and Visualize in DbSchema | DbSchema
Learn how to visualize MongoDB relationships with embedding, references, one-to-many patterns, and DbSchema diagrams. Decide when to embed vs reference.
Database Design Errors to Avoid & How To Fix Them
Six database design mistakes that cost you later: foreign keys, indexes, JSON columns, normalization, naming and documentation, with the fix for each.
Best ER Diagram Tools in 2026: Free and Paid Comparison | DbSchema
Compare the best ER diagram tools in 2026 for PostgreSQL, MySQL, SQLite, MongoDB, and multi-database teams. Visual design, reverse engineering, and documentation.
PostgreSQL Transactions Guide with COMMIT and ROLLBACK | DbSchema
BEGIN, COMMIT, ROLLBACK and SAVEPOINT run on PostgreSQL 18: the aborted transaction block, isolation levels, and the commands that cannot run inside a transaction.
ERD Diagrams | MySQL Database Design and Docs with DbSchema
Connect DbSchema to MySQL, read the schema as an ER diagram, export HTML5 documentation, keep the model in Git and sync it with the database.
MySQL Create User: CREATE USER, GRANT, Roles, and Host Examples | DbSchema
Learn MySQL CREATE USER and GRANT syntax for 5.7, 8.0, and 8.4, including localhost, wildcard hosts, roles, and secure privilege examples.
MySQL CREATE TABLE Guide with Examples | DbSchema
Learn how to create tables in MySQL with SQL commands, prerequisites, and visual design steps in DbSchema.