Module 2 Flashcards
Is it true that end users find it difficult to think of a relation as a table?
True
It is perceived as a two-dimensional structure composed of rows and columns. What is this structure called?
Table
E. F. Codd used the terms ‘relation’ and ________ as synonyms.
Table
You can think of a table as a persistent representation of a logical relation— that is, a ________ whose contents can be permanently saved for future use.
Relation
A table that contains a group of related entity occurrences is called an ________.
Entity Set
In the relational model, ______ is/are important because they are used to ensure that each row in a table is uniquely identifiable.
Keys
A ________ consists of one or more attributes that determine other attributes.
Key
The relationship is called ___________, which means that the value of one or more attributes determines the value of one or more other attributes.
Functional Dependence
The attribute whose value determines another is called a ________.
Determinant
The attribute whose value is determined by the other attribute is called ________.
Dependent
A table is perceived as a two-dimensional structure composed of rows and columns. Is this statement true?
True
Can a table row (tuple) represent multiple entities at the same time?
False
Each table column represents an attribute, and each column has a distinct name. Is this statement true?
True
Each intersection of a row and column represents a multiple data value. Is this statement true?
False
All values in a column must conform to the same data format. Is this statement true?
True
Each column has a specific range of values known as the ________.
Attribute domain
The order of the rows and columns is immaterial to the DBMS. Is this statement true?
True
Which of the following statements about Entity Integrity and Referential Integrity is TRUE?
A Foreign Key (FK) must always reference an existing Primary Key value or be null.
What best describes Entity Integrity?
A Primary Key ensures each row has a unique identity and cannot be null.
What best describes the Referential Integrity Rule?
A Foreign Key must reference an existing Primary Key value or be null.
One of the set operators that is referred to as a unary operator because it only uses one table as input is ________.
Select
One of the set operators that yields all values for selected attributes is called ________.
Project
One of the set operators that combines all rows from two tables, excluding duplicate rows is called ________.
Union
One of the set operators that yields only the rows that appear in both tables is called ________.
Intersect
One of the set operators that yields all rows in one table that are not found in the other table is called ________.
Difference
One of the set operators that yields all possible pairs of rows from two tables is called ________.
Product
One of the set operators that allows information to be intelligently combined from two or more tables is called ________.
Join
One of the set operators that links tables by selecting only the rows with common values in their common attribute(s) is called ________.
Natural Join
It provides a detailed description of all tables in the database created by the user and designer. What is this called?
Data Dictionary
This relationship is the norm for relational databases. What is it?
1:M
This relationship can be related to only one other entity, and vice versa. What is it?
1:1
This relationship is not supported directly in the relational environment. What is it?
M:N
This is a detailed, logical representation of the data for an organization or for a business area. What is it called?
entity-relationship model
Who first introduced the ER data model and in what year?
Peter Chen_1976
It was defined as anything about which data will be collected and stored. What is this?
Entity
Each entity consists of a set of attributes that describes particular characteristics of the entity. Is this statement true?
True
The ERM uses _______—one or more attributes that uniquely identify each entity instance.
Identifiers
An attribute that can have only a single value is called ________.
Single-valued attributes
These are attributes that can have many values. What are they called?
Multivalued Attributes
An attribute whose value is calculated from other attributes is called ________.
Derived Attribute
What describes associations among data?
Relationships
What is used to describe the relationship classification?
connectivity
It expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity. What is this called?
Cardinality
It indicates the number of entities or participants associated with a relationship. What is this called?
Relationship Degree
What exists when an association is maintained within a single entity?
unary relationship
What exists when two entities are associated?
binary relationship
What exists when three entities are associated?
ternary relationship
