How does column-oriented NoSQL differ from document-oriented?

Question

The three types of NoSQL databases I've read about is key-value, column-oriented, and document-oriented.

Key-value is pretty straight forward - a key with a plain value.

I've seen document-oriented databases described as like key-value, but the value can be a structure, like a JSON object. Each "document" can have all, some, or none of the same keys as another.

Column oriented seems to be very much like document oriented in that you don't specify a structure.

So what is the difference between these two, and why would you use one over the other?

I've specifically looked at MongoDB and Cassandra. I basically need a dynamic structure that can change, but not affect other values. At the same time I need to be able to search/filter specific keys and run reports. With CAP, AP is the most important to me. The data can "eventually" be synced across nodes, just as long as there is no conflict or loss of data. Each user would get their own "table".

Answer 1

The main difference is that document stores (e.g. MongoDB and CouchDB) allow arbitrarily complex documents, i.e. subdocuments within subdocuments, lists with documents, etc. whereas column stores (e.g. Cassandra and HBase) only allow a fixed format, e.g. strict one-level or two-level dictionaries.