Every Java developer has written this loop: fetch a list, then for each row fetch its related data. One query becomes a thousand. You faked a JOIN with a "for" loop — because the ORM made the real thing easy to avoid.

First rule of JOIN Club: the database is better at this than your code. For two decades, the ORM handled the SQL — now AI finishes the job, generating queries you skim and ship. While underneath you have an SQL you can no longer read.

This talk gives you working SQL literacy — enough to read a query, judge whether it's right, and know when your ORM has ran out of road. We start with joins, what they actually do. Then the SQL what ORM hid — CTEs, window functions, recursive queries that walk a tree in one statement, multisets.

You won't leave an SQL expert. You'll leave able to read what your tools write, prompt for the right query, and spot where the ORM ends. For Java developers comfortable with basic "SELECT" and an ORM.