5 sql tutorials
Hands-on SQL tutorials, walkthroughs, and reference guides written by practitioners.
A practical guide to relational algebra covering fundamental operators, join types, and derived operations, with SQL comparisons and examples that show how database engines process queries internally.
Learn how to use the SQL RANK() function to assign rankings to rows, handle ties, and compare it with DENSE_RANK() and ROW_NUMBER().
Learn how correlated subqueries do row-by-row comparisons in SQL. Discover use cases and how they differ from JOINs, window functions, or non-correlated queries.
A practical guide to relational algebra covering fundamental operators, join types, and derived operations, with SQL comparisons and examples that show how database engines process queries internally.
Master SQL data types in MySQL, PostgreSQL and SQL Server. Learn to choose the right numeric, text, and date formats to optimize performance and data integrity.
Understand how SQL ON DELETE RESTRICT protects data integrity. Learn how it blocks unsafe deletes and when to choose it over CASCADE or SET NULL rules.
Dario Radecic
Allan Ouko
Amberle McKee