Re: avoiding Long SQL statements
As for processing multiple queries: think about it, each time a single query needs processing, it's sent to the server, the results are sent back where you process them yourself in your application layer. That's multiple times of overhead for parsing the queries, running the optimizer to create a queryplan, and generating network traffic. It's much more efficient to run just one single query, and its quite common to spend some time on crafting that query. And, congratulations, instead of maintaining some 5 line queries, you are maintaining 10s at the very least, but more probably hundreds of lines of php code that do the post query processing.
I just want to add, that if you are in a situation where you'd have multiple php pages that use the same, complicated join query or queries again and again, you can put that in a VIEW if you are running mysql >= 5. That does not prevent you from maintaining it, but it does ensure that there's a single point of definition, thats stored in a place where it belongs, e.g. the database.