Duplicate Data

This is often a problem in databases. Duplicate means there are two records with the same data.

These are some of the problems with duplicate data:

> Making a change can be confusing as you think you have made a change, but the old (duplicated) data still turns up
> Waste of storage space
> Data set larger than it needs to be, so making queries slower.
> "Referential Integrity" rules broken because more than one record exists for the same primary key. You can often set a "Enforce Referential Integrity" feature in the database to prevent this.

2020-10