The Data Mining, Essay Example

Why are there so many more foreign keys in the third normal form than in the first?

In second normal form, tables were created for all data related to the data contained in the first table (Date, 1999).

Is this always going to be true?

No, but it usually is (Freetutes.com, 2011).

Why is it important to define the primary keys of a file correctly?

They are necessary for relational binding on from master to slave tables (Kent, 1983).

What happens to the third normal form when they are incorrectly defined?

The relationships will be wrong (Date, 1999).

Some designers will say that to make an address file into third normal form, you should take out the city and state, place it into a different table, and link it by zip code. What advantages and disadvantages are there to this?

The advantage is that it eliminates maintaining repetitive city, state, and zip data for each record (Freetutes.com, 2011).

The disadvantage is that a location may not follow the city, state, zip pattern strictly (Kent, 1983).

When normalizing a table that can have a many-to-many relationship with another table, what steps should you take?

Identify primary keys in tables (Date, 1999).

Create a composite table of foreign keys (Freetutes.com, 2011).

Link the primary keys to the forgeign keys of the composite table (Kent, 1983).

What are the advantages of third normal form for applications with a lot of changes to the database, such as a data entry program?

The advantage is that data integrity is maintained (Date, 1999).

What are the disadvantages of third normal form for an application that does a lot of reporting on a stable database like general ledger month-end reporting?

The disadvantage is that complex queries must be configured to report the appropriate data (Freetutes.com, 2011).

References

Date, C. J. (1999). An Introduction to Database Systems (8th ed.). Addison-Wesley Longman.

Freetutes.com (2011). Systems analysis and design: Complete introductory tutorial for software engineering. Freetutes.com. Retrieved from http://www.freetutes.com/systemanalysis/

Kent, W. (1983). A Simple Guide to Five Normal Forms in Relational Database Theory, Communications of the ACM, 26: 120–125.