What is a relational database?
A relational database is a kind of database with pre-defined relationships between data items. The relational database organizes items as a set of relational tables (columns and rows) that are often queried by SQL. The tables have information about how data points are related to other data points in the database.
In a relational database (or SQL database), each table row can be tagged with a unique identifier or primary key. Foreign keys are used for relating the rows among several tables. The data in a relational database can be accessed in lots of different ways without having to reorganize the database tables.