Chapter 3. The Relational Database Model

Question 1

It enables you to view data logically rather than physically

Answer 1

Relational Model

Question 2

Characteristics of a Relational Model

Answer 2

1. A table is perceived as a two-dimensional structure composed of rows and columns.
2. Each table row (tuple) represents a single entity occurrence within the entity set.
3. Each table column represents an attribute, and each column has a distinct name.
4. Each intersection of a row and column represents a single data value.
5. All values in a column must conform to the same data format.
6. Each column has a specific range of values known as the attribute domain.
7. The order of the rows and columns is immaterial to the DBMS.
8. Each table must have an attribute or combination of attributes that uniquely
   identifies each row.

Question 3

One or more attributes that determine other attributes.

Answer 3

Key

Question 4

Subject Code, Student number, Philippine national id number are examples of?

Answer 4

Key

Question 5

The role of a key. In the context of a database table, the statement “A determines B” indicates that knowing the value of attribute A means that the value of attribute B can be looked up.

Answer 5

Determination

Question 6

Within a relation R, an attribute B is ___ dependent on an attribute A if and only if a given value of attribute A determines exactly one value of attribute B.

Answer 6

Functionally/Functionally Dependent

Question 7

Any attribute in a specific row whose value directly determines other values in that row

Answer 7

Determinant

Question 8

Any attribute in a specific row whose value directly determines other values in that row

Answer 8

Determinant

Question 9

An attribute whose value is determined by another attribute.

Answer 9

Dependent

Question 10

A condition in which an attribute is functionally dependent on a composite key but not on any subset of the key.

Answer 10

Full Functional Dependence

Question 11

In the relational model, an identifier composed of one or more attributes that uniquely identifies a row.

Answer 11

Primary Key

Question 12

A multiple-attribute key

Answer 12

Composite Key

Question 13

An attribute that is part of a primary key.

Answer 13

Key Attribute

Question 14

An attribute or attributes that uniquely identify each entity in a table

Answer 14

Super Key

Question 15

A minimal superkey; that is, a key that does not contain a subset of attributes that is itself a superkey.

Answer 15

Candidate Key

Question 16

Types of Keys

Answer 16

• Primary Key
• Composite Key
• Super Key
• Attribute Key
• Foreign Key
• Secondary Key

Question 17

The property of a relational table that guarantees each entity has a unique value in a primary key and that the key has no null values.

Answer 17

Entity Integrity

Question 18

The absence of an attribute value.

Answer 18

Null

Question 19

A null is not a blank.

Answer 19

True

Question 20

An attribute or attributes in one table whose values must match the primary key in another table or whose values must be null.

Answer 20

Foreign Key

Question 21

A condition by which a dependent table’s foreign key must have either a null entry or a matching entry in the related table.

Answer 21

Referential Integrity

Question 22

An attribute or combination of attributes that uniquely identifies each row in a table

Answer 22

Primary Key

Question 23

A minimal (irreducible) superkey; a superkey that does not contain a subset of attributes that itself is a super key

Answer 23

Candidate Key

Question 24

A candidate key selected to uniquely identify all other attributes that itself is a super key

Answer 24

Primary Key

Question 25

A candidate key selected to uniquely identify all other attributes that itself is a super key

Answer 25

Primary Key