How can an SQL query return data from multiple tables is tagged php, but it's really all about SQL in general, and MYSQL in particular. None of the answers mention PHP or include any PHP code.
I believe the author tagged it with PHP because:
Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer.
I would otherwise remove the PHP tag, but that note gives me pause. Should the PHP tag be removed from this question?