Chapter 5 Norm questions-1_2

Chapter 5 Norm questions-1_2 - Chapter 5 Normalization of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 5 Normalization of Database Tables Answers to Review Questions 1. What is normalization? Normalization is the process for assigning attributes to entities. Properly executed, the normalization process eliminates uncontrolled data redundancies, thus eliminating the data anomalies and the data integrity problems that are produced by such redundancies. Normalization does not eliminate data redundancy; instead, it produces the carefully controlled redundancy that lets us properly link database tables. 2. When is a table in 1NF? A table is in 1NF when all the key attributes are defined (no repeating groups in the table) and when all remaining attributes are dependent on the primary key. However, a table in 1NF still may contain partial dependencies, i.e., dependencies based on only part of the primary key and/or transitive dependencies that are based on a non-key attribute. 3. When is a table in 2NF? A table is in 2NF when it is in 1NF and it includes no partial dependencies. However, a table in 2NF may still have transitive dependencies, i.e., dependencies based on attributes that are not part of the primary key. 4. When is a table in 3NF? A table is in 3NF when it is in 2NF and it contains no transitive dependencies. 7. What is a partial dependency? With what normal form is it associated? A partial dependency exists when an attribute is dependent on only a portion of the primary key. This type of dependency is associated with 1NF. 8. What three data anomalies are likely to be the result of data redundancy? How can such anomalies be eliminated? The most common anomalies considered when data redundancy exists are: update anomalies, addition anomalies, and deletion anomalies. All these can easily be avoided through data normalization. Data redundancy produces data integrity problems, caused by the fact that data entry failed to conform to the rule that all copies of redundant data must be identical. 9. Define and discuss the concept of transitive dependency.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Transitive dependency is a condition in which an attribute is dependent on another attribute that is not part of the primary key. This kind of dependency usually requires the decomposition of the table containing the transitive dependency. To remove a transitive dependency, the designer must perform the following
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/22/2011 for the course ITC 101 taught by Professor Cuibap during the Three '11 term at Charles Sturt University.

Page1 / 8

Chapter 5 Norm questions-1_2 - Chapter 5 Normalization of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online