4.3 Relational Databases and Normalisation

Where data is held in tables in a relational database

• A process used to come up with the best possible design for a database • Tables should be organised so that data is not duplicated in the same table or in indifferent tables • The structure should allow complex queries to be made

1NF, 2NF, 3NF

• Contains no repeating attributes or groups of attributes • All attributes must be atomic - a single attribute cannot consist of 2 data items such as firstname and surname

• 1NF and contains no partial dependencies • Can only occur if the primary key is a composite key

Contains no non-key dependencies

• Easier to maintain and change • No unnecessary duplication of data • Data integrity is maintained • Having smaller tables with fewer fields means faster searches and savings in storage