This module covered database normalization up to 2NF or second normal form.
It identified the requirements of, and procedures for reaching, 1NF and 2NF.
Along the way, it introduced the concepts of normalization, repeating groups, and functional dependencies.
Having completed this module, you should now be able to:
Although second normal form eliminates problems from many relations, you will occasionally run into relations that are in second normal form yet still exhibit anomalies.
Assume, for example, that each new DVD title that DistributedNetworks carries comes from one distributor and that each distributor has only one warehouse that has only one phone number.
The following relation is therefore in second normal form:
Item (item_numb, title, distrib_numb, warehouse_phone_number)
For each item number, there is only one value for the item's title, distributor, and warehouse phone number.
The following anomalies exist:
- There is one insertion anomaly: You cannot insert data about a distributor until you have an item from that distributor.
- There is one deletion anomaly: If you delete the only item from a distributor, you lose data about the distributor.
- There is also a modification anomaly: The distributor's warehouse phone number is duplicated for every item the company gets from that distributor.
The relation is in second normal form but not third.
Before you move on to the next module, take the following quiz to check your knowledge of normalization to 2NF.
Normalization - Quiz