What is an example of a non-relational database? Where/how are they used?

database, non-relational-database

Solution

- Flat file

- CSV or other delimited data

- spreadsheets

- /etc/passwd

- mbox mail files

- Hierarchical

- Windows Registry

- Subversion using the file system, FSFS, instead of Berkley DB

Problem

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: - Database system that is not relational. - Good reasons NOT to use a relational database?

Original source

Related problems