SQL JOIN and different types of JOINs

Question

What is a SQL JOIN and what are different types?

Answer 1

I'm going to push my pet peeve: the USING keyword.

If both tables on both sides of the JOIN have their foreign keys properly named (ie, same name, not just "id) then this can be used:

SELECT ...
FROM customers JOIN orders USING (customer_id)

I find this very practical, readable, and not used often enough.