Have you ever heard from CTEs or Window functions? What is it and when and how to use it? Can you remember correlated subselects? The talk shows some fancy SQL commands that you can use with PostgreSQL, MariaDB and MySQL.
SQL just has 14 commands ... but these can get very complex. Also since a few years there are some very useful new functionalities like CTEs and Window functions. Additionally the talk shortly will show correlated subselects and more.