Definition of a Derivative Attribute
So-called derivative attributes violate the rules of normalization in relational theory because they are not atomic. A derivative attribute is any attribute that can be derived by calculation from other data in the model.
The issue of derivative attributes should not concern you during the logical design phase other than knowing that they should not be modeled. Derivative attributes are an important consideration for physical database design, where they are often modeled as a means for enhancing system performance.
Note that Teradata Database offers several features like hash and join indexes, aggregate join indexes, and global temporary tables that lessen the temptation to denormalize the physical design of your base tables by using derivative attributes.