#native_company# #native_desc#

Database Normalization and Design Techniques Page 3

By Barry Wise
on July 31, 2000

Second Normal Form

  1. Create separate tables for sets of values that apply to multiple records.
  2. Relate these tables with a foreign key.

We break the url values into a separate table so we can add more in the future without having to duplicate
data. We’ll also want to use our primary key value to relate these fields:

userId name company company_address
1 Joe ABC 1 Work Lane
2 Jill XYZ 1 Job Street
urlId relUserId url
1 1 abc.com
2 1 xyz.com
3 2 abc.com
4 2 xyz.com

Ok, we’ve created separate tables and the primary key in the users table, userId, is now related to the foreign key in
the urls table, relUserId. We’re in much better shape. But what happens when we want to add another employee of
company ABC? Or 200 employees? Now we’ve got company names and addresses duplicating themselves all
over the place, a situation just rife for introducing errors into our data. So we’ll want to look at applying the Third Normal Form: