SQL (Structured Query Language) databases have been a primary data storage mechanism for more than four decades. Usage exploded in the late 1990s with the rise of web applications and open-source options such as MySQL, PostgreSQL and SQLite.

NoSQL databases have existed since the 1960s, but have been recently gaining traction with popular options such as MongoDB, CouchDB, Redis and Apache Cassandra.

Some projects are better suited to using an SQL database. Some are better suited to NoSQL. Some could use either interchangeably.

Some SQL databases are adopting NoSQL features and vice versa. The choices are likely to become increasingly blurred, and NewSQL hybrid databases could provide some interesting options in the future.