SQLite is a pretty neat single-file database engine. In their own words,

SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. SQLite is the most widely deployed SQL database engine in the world. The source code for SQLite is in the public domain.

There are SQLite libraries and interfaces available for pretty much any software language, but they also include sqlite3, which is “a terminal-based front-end to the SQLite library that can evaluate queries interactively and display the results in multiple formats. sqlite3 can also be used within shell scripts and other applications to provide batch processing features.”

If you have experience writing SQL queries, it’s easy to get started with the SQLite interface. A few non-standard commands that will help you get started are .tables , which lists the names of all tables in the current database, and .schema tablename which describes the schema of the named table. From there, you can use traditional SQL queries to add, modify, and delete rows in your tables. Have fun!

Note: Be sure to do a backup of your database file before mucking about with the sqlite3 interface, sometimes the program crashes, or you might type a dangerous command or something like that.