I've been reading up on NoSQL, but I can't figure out one thing. Is it meant to be a replacement for traditional SQL, or is it meant to be used in conjunction with it?
Basically, what I'm asking (I think) is: if you have some structured data that could be represented in an SQL database with tables for each kind of object and connections between them (e.g. users, messages, friendships, whatever), are there any advantages / does it make sense to store all of it in a NoSQL database, or should you just store it in a traditional SQL database and use a NoSQL one just for the stuff that needs to be accessed more frequently (e.g. cache)?