Recently, there has been a lot of buzz about “No SQL” databases. In fact there are at least two conferences on the topic in 2009, one on each coast. Seemingly this buzz comes from people who are proponents of:
• document-style stores in which a database record consists of a collection of (key, value) pairs plus a payload. Examples of this class of system include CouchDB and MongoDB, and we call such systems document stores for simplicity
• key-value stores whose records consist of (key, payload) pairs. Usually, these are implemented by distributed hash tables (DHTs), and we call these key-value stores for simplicity. Examples include Memcachedb and Dynamo.
In either case, one usually gets a low-level record-at-a-time DBMS interface, instead of SQL. Hence, this group identifies itself as advocating “No SQL.”
Great first part of a two-part series about data storage and how "NoSQL" doesn't at all get at what things like CouchDB, MongoDB, etc. are all about.