What is a relational database
A database with more than one table where the data in the fields is linked by using the primary key from one table as a foreign key in another table is a relational database.
Below is an extract of a database for players on each of a football clubs teams. With all of the data in the example below in one table we have data that is written out more than one time. This is known as redundant
data. Each time it is entered there is a chance a mistake will be made like in the example where the team name has been spelled incorrectly. When two pieces of data that should be the same in a database are different it is known
as data inconsistency.
In the example above the single table database has been split into a relational database. The team name is now only entered once and so consistent throughout. You can still find out the team name and colours for a player
because the tables are liked by the primary key from the teams table, team ID, appearing as a foreign key in the player table.