Sql

Learn core SQL with PostgreSQL-friendly examples: filtering, aggregates, joins, CTEs, and the habits that transfer to real application databases.

Use EXPLAIN, index design, and query rewrites to find and fix slow MySQL queries—plus the mistakes that keep databases sluggish.

Understand SQL Server deadlocks, pull the deadlock graph fast, and fix the code patterns behind error 1205 before they come back. Learn what to change first.