SQL Indexing and Tuning e-Book
use-the-index-luke.com
use-the-index-luke.com
I very much like resources like this that explain things by explaining how they are implemented. Once you understand the basics of how a database is implemented, a lot of the performance implications of your queries make sense.
It also really helps in the understanding of what is going on in EXPLAIN output.
It's an entire book, so it's tough to say in a small comment box.
If you're doing queries across a 5MB database on a phone, you should be fine with or without optimizations.
In fact, the only way you could distribute the contents is by having an identical mirror to the site.
Perhaps you really meant to complain that it isn't Free?