An example of a non-relational database? Where/how are they used


I have been working with relational databases for sometime, but it only recently occurred to me that there must be other types of databases that are non-relational.

What are some examples of non-relational databases, and where/how are they used in the real world? Why would you choose to use a non-relational database over relational databases?

Edit: Two other similar questions have been mentioned in the answers:

Best Answer

An admittedly obscure but interesting alternative to the types of databases mentioned here is the associative database, such as Sentences, from LazySoft Technology. There is a free personal version you can download and try on your own. The Enterprise Edition is also free, but requires a request to the company.

Essentially, an associative database allows you to store information in much the same way as our brains do: as things and associations between those things. The name "Sentences" comes from the way this information can be represented in a subject-verb-object syntax:

  • Tom is brother to Laura
  • San Francisco is located in California
  • Mike has a credit limit of $10,000

A sentence may be the subject or object of another sentence:

  • (Bus 570 arrives at 8:15am) on Sundays
  • Mary says (the pie was baked by William)

So, everything can be boiled down to entities and associations.

There is, of course, much more to Sentences than what can be expressed here. I recommend that you take some time to read more about it in a white paper from LazySoft.

"The Associative Model of Data" is a book available in PDF format by Simon Williams, one of the creators of Sentences.