What are the differences between the NoSQL databases and how are they different from traditional relational databases?

Question

There seem to be a lot of new "NoSQL" type databases out there. Some of the popular ones are CouchDB, Cassandra and MongoDB.

What are the differences between such databases and how are they different from tradition relational databases? What are the advantages and disadvantages of picking NoSQL DBs over SQL DBs?

Answer 1

The term NoSQL covers a lot of different approaches to data storage ranging from the simplest key/value storage to sophisticated document databases. It's a catchy buzz word, but not very discriptive IMHO.

For a quick intro you could take a look at the Wikipedia entry for NoSQL