If you are doing some data logging, sensor reading or other routine task with raspberry Pi, then you probably are thinking of using database. The list of database software choices is quite long, but in most cases you will end with single or few tables in database. First thought might be MySQL – well known database server in WWW. Anyway this is pretty heavy tool to have running on Raspberry Pi. In my opinion SQLite is probably most suitable choice. Because it is serverless, lightweight, opensource and support most SQL code. Another handy thing is that SQLite stores data in single file which can be stored anywhere.