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.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Duplicate Data