As databases evolve, learning how to get the best out of the different solutions out there is the key to understanding and extracting the data in the way you need from your required data store. Document databases, like MongoDB, CouchDB, Couchbase Server and many others provide a completely different model and set of problems for interfacing and extracting data.
You need to be able to understand your structure, how you can query the information, and how to perform different data mining techniques on what is very obviously a completely different structure of information.
In this article, I try to take you through the basics of data mining when using a document database.
Read: Data mining in a document world