Data Redundancy

A database term.

Data redundancy in a database means that the same data is present in more than one table. Or in the case of a flat file database, there are records with partly duplicated data. For example

Jones, 48, Male, Teacher
Jones, 48, 3 Advent Drive
Jones, employee number 22345

As you can see in the records above, the name is repeated three times and the age is duplicated twice. A relational database can avoid this duplication.

This is usually a mark of an inefficient database and people go to great lengths to avoid it.

In order to reduce duplicated data, you can use the three 'normal forms' of database design i.e. First Normal, Second Normal and the most efficient (but complex) Third Normal Form.

2020-10