Question

416. Why is the relational model important?
416. List the characteristics a table must have to be considered a relation. Define the term domain, and explain the significance of the domain integrity constraint to a relation.
416. Give an example of a relation (other than one from this chapter).
416. How do surrogate keys obtain their values?
416. Explain three possible interpretations of a null value.
416. In your own words, describe the nature and purpose of the normalization process.
416. Study the following tables, then transform into 1NF:

   

Lname	Fname
Jack	Mary, Maria, Maya
Mathews	Don, Donald, Jack

416. Study the following tables, then transform into 1NF:

Name	Weight
Michael	87 kg
Gabriel	92 lb
Nancy	65 kg
Alice	145 lb

416. Study the following table, then transform into 2NF:

Student	Course_ID	Grade	Address
Nancy	CIS331	A	80 ABC Av.
Erik	CIS331	B	100 DEF ST.
Sam	CIS331	C	66 GHI ST
Nat	CIS350	A	90 JKL RD

10790. Study the following table, then transform into 3NF:

Student	Course_ID	Grade	Letter_Grade
Nancy	CIS331	A	4.0
Erik	CIS331	B	3.0
Sam	CIS331	C	2.0
Nat	CIS350	A	4.0

Answer 1

Solution

Why is the relational model important?

It is the single most important standard in database processing and is used for the design and implementation of almost every commercial database worldwide

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List the characteristics a table must have to be considered a relation.

• Rows contain data about an entity.
• Columns contain data about attributes of the entity
• Cells of the table hold a single value.
• All entries in a column are of the same kind.
• Each column has a unique name.
• The order of the columns is unimportant.
• The order of the rows is unimportant.

A domain is a collection of like items (such as integers), and a domain integrity constraint enforces the fact that all column values come from the same domain.

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Give an example of a relation (other than one from this chapter).

Example: TEXTBOOK (ISBN, Title, Publisher, Copyright)

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How do surrogate keys obtain their values?

They are supplied automatically by the DBMS.

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Explain three possible interpretations of a null value.

Three possible interpretations are:

• Value not appropriate
• Value known to be blank
• Value appropriate and unknown

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In your own words, describe the nature and purpose of the normalization process.

The purpose of the normalization process is to prevent update problems in the tables (relations) in the database.

The nature of the normalization process is that we break up relations as necessary to ensure that every determinant is a candidate key.

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