“Calculating distance using MySQL” is a very useful blog post for everyone who works with geographical location data and MySQL. It shows a simple example of how to calculate the distance between two coordinates on a sphere (Earth in particular) within the MySQL itself.
This is probably way too far out for most people using MySQL for their web applications. But it does highlight the technical complexity of running high load web applications, and how some of the issues can be solved or worked around.
Metabase is an Open Source business intelligence and analytics tool. It supports a variety of databases and services as sources for data, and provides a number of data querying and processing tools. Have a look at the GitHub repository as well.
And if you want a few alternatives or complimenting tools, I found this list quite useful.