What, if anything, is wrong with this query:

SELECT c$.$customer$\_$name, o$.$order$\_$date, o$.$order$\_$amount FROM customers c JOIN orders o ON o$.$order$\_$number $=$ o$.$order$\_$number WHERE c$.$customer$\_$city $=$ 'San Diego';

The city attribute was not included in the Select clause

This will result in a Cartesian product where customers will be mismatched with orders

Strings are enclosed in double quotes, not single quotes

There is nothing wrong with this query

You need to use the LIKE operator with character data