Relational Database Fundamentals

A one-to-one relationship is represented by which of the following notations?

1:1

In Ken's Travel database, the Reservations table and the Customers table have a common field by which they can be joined and queried. What type of constraint will ensure the consistency of data between these tables?

A referential integrity constraint

In a data model, details about how the data will be kept accurate are described by which type of information?

Integrity information

In terms of database relationships, what determines the cardinality of a relationship?

The mapping of instances of one entity to another

When like-named columns appear in multiple tables, and the same data manipulation process needs to access those columns, the name of the column is preceded by what?

The name of the table, followed by a period as a separator

According to E.F. Codd, which three pieces of information are needed to retrieve a value?

The name of the table, the name of the column, and the primary key of the row

In terms of database relationships, what determines the degree of a relationship?

The number of entities involved in the relationship

When a table field contains a null value, that value may be understood to be ______.

unknown

A one-to-many relationship is represented by which of the following notations?

1:n

Which of the following is true of columns in a relation?

Columns must have a name that is unique within its relation.

Who developed entity-relationship (ER) modeling?

Peter P. Chen

What part of a nonprocedural DML retrieves data from a database?

Query language

What is wrong with the following SQL statement?

The c_num attribute is ambiguous in the first line of the statement.

How are the tables that make up the data dictionary updated?

They are updated automatically by the DBMS as the system is used.

Ted has created a database relation named Customers. It contains the following fields: c_id, first_name, last_name, dob. There are currently 20 tuples in the relation. What is the cardinality of the Customers relation?

Twenty

David has created a binary relationship in his Tsunami database. This type of relationship involves how many tables?

Two

In what type of computing environment does a high-performance PC present the user interface, run the application logic and access the corporate database, which is usually located on a separate server?

Two-tier using fat client

Which of the following is true of views?

Views permit customized access to data.

A conceptual, high-level description of the structure of a database is contained in:

an entity-relationship (ER) model.

Which of the following is a characteristic of entities?

All entities will have unique identifiers.

Amanda is designing a relation. As she starts to consider sample data, she discovers that one attribute within a row needs to have more than one value. What should Amanda do about the design of the relation?

Amanda should redesign the relation so that each attribute will have only one value in any given row.

What is a fat client?

A client that performs the bulk of the data-processing operations

Which of the following is an example of a domain constraint?

A data type

In a relational database, what is an attribute?

A column

Consider the DBDL statement in the exhibit. The highlighted portion of the statement is an example of which of the following?

A domain constraint

In his Travel database, Ken has applied a constraint to the plane_type attribute in the Flights table restricting the type of airplane that can be specified to one of a list of seven different aircraft. What type of constraint has Ken applied?

A domain constraint

Which of the following statements about primary and foreign keys is correct?

A foreign key can reference only one parent key, and multiple foreign keys can reference the same parent key value.

Which of the following is true of rows within a relation?

A row will always be unique.

In a three-tier architecture, which component typically controls which user can access the database?

Database server

What does a set of permissible values for one or more attributes in a relational database referred to as?

Domain

Ellen is a temporary employee who was hired to update the telephone and fax numbers of several hundred clients in the company database. In order for Ellen to access the required data, a data manipulation process creates a view for her named Temp_Input. Ellen then makes her data changes to the Temp_Input table. Which of the following can be said about Ellen's access to the data?

Ellen accesses the data through a virtual table.

What are entities?

Entities are logical categories that make up a database, as opposed to the actual data items that inhabit the entity.

The process of organizing and refining relations within a relational database is known as what?

Normalization

A many-to-many relationship is represented by which of the following notations?

m:n

Antoinette is creating a database of recipes used in her restaurant. She is designing the Recipe table, which includes the following fields: recipe_id, recipe_name, recipe_type and recipe_author. Which attribute would best serve as the primary key for the Recipe relation?

recipe_id

How many tables are involved in a ternary relationship?

Three

As David is reviewing the data model for his tsunami database, he identifies a relationship in which for each instance of entity A, there are zero or more instances of entity B, and for each instance of entity B, there are zero or more instances of entity A. What is the cardinality of the relationship David has identified?

Many-to-many

Consider the information engineering (IE) diagrams shown in the exhibit. The primary key of the Phone relation, phone_id, is a foreign key in the Employee relation. What can be said about the relations shown in the exhibit?

The Employee relation is a strong entity and the Phone relation is a weak entity.

In regard to database relations, what is meant by the cardinality of a relation?

The cardinality of a relation is the number of tuples it contains.

An entity that must reference another entity for its data to be meaningful is what type of entity?

Weak entity

David wants to limit Ken's ability to modify data in his Tsunami database. Which subset of Structured Query Language (SQL) can he use to restrict the operations that Ken will be allowed to perform?

Data Control Language (DCL)

David needs to create a database and tables. Which of the following will he use?

Data Definition Language (DDL)

Schemas, views, tables and indexes can be created using which of the following?

Data Definition Language (DDL)

What is a thin client?

A client that relies on the server to perform the bulk of the data-processing operations

Every column in a relation must have what?

A defined domain

Which of the following is an example of an entity constraint?

A rule stating that no part of the primary key can be null

How are views stored within a database?

As named database operations

What is a column in a table that is the primary key of another table known as?

Foreign key

Ted has created a database relation named Customers. It contains the following fields: c_id, first_name, last_name, dob. There are currently 20 tuples in the relation. What is the degree of the Customers relation?

Four

Where does the true power of a relational database lie?

In the relationships that are created between tables

Which of the following most accurately describes a relational database?

It includes multiple tables of interrelated data.

Which of the following is an advantage to using a nonprocedural DML?

It is easier for the user.

The number of tuples in a relation determines which characteristic of the relation?

Its cardinality

The number of attributes in a relation determines which characteristic of the relation?

Its degree

In a data model, details about the kinds of operations that are permitted on the data are described by which type of information?

Manipulative information

Which of the following correctly characterizes databases?

Most modern databases share a set of characteristics.

Which of the following processes may reduce the duplication of data items within a database, yet increase the number of tables within it?

Normalizing

A unary relationship involves how many tables?

One

As David is reviewing the data model for his tsunami database, he identifies a relationship in which for each instance of entity A, there are zero or more instances of entity B, but for each instance of entity B, there is only one entity A. What is the cardinality of the relationship that David has identified?

One-to-many

Consider the information engineering (IE) diagram in the exhibit showing the relations Excavations and Finds. What is the relationship between Excavations and Finds?

One-to-many

In reviewing your data model, you discover that you have a relationship in which for each instance of entity A, there is no more than one entity B. What is the cardinality of the relationship?

One-to-one

In a relational database, what is a tuple?

Record

What is the underlying concept of the client-server system?

Separation of tasks

In a data model, a set of rules by which a database can be built is described by which type of information?

Structural information

Which of the following is a characteristic of tables in a relational database?

Tables usually contain data that relates to data in other tables in some way.

David is creating a table to track tsunami activity in the South Pacific. He has created a column called "t_id" which will serve as the primary field for his table. Which of the following rules will apply to the "t_id" field?

Values in the t_id field must be unique and must not be null.

In a relational database, rows, columns and tuples are stored in:

a relation.

In a relational database, a relation is another name for:

a table.

In what type of computing environment does the terminal present the user interface, while the database, the transaction processing and the application programming are all resident on one separate host computer?

Centralized mainframe with terminal client

Ken wants to use a subset of SQL to insert data into several of his database tables. Which subset of SQL should he use?

Data Manipulation Language (DML)

Which part of a relational database describes the basic elements of the database?

Data dictionary

Which of the following is a formal expression of data, data relationships, and constraints on the data?

Data model

What is an advantage of three-tier client-server systems over two-tier client-server systems?

The centralized application logic makes maintaining the application easier.

David is designing a database to track tsunami activity worldwide. He is currently in the process of identifying valid primary keys for his tables and he cannot identify a single column in his Magnitude table that can serve as a primary key. In determining a good composite key, what should David keep in mind?

The composite key should be made up of the least number of columns necessary to ensure uniqueness.

Which of the following is true of databases in a centralized, mainframe environment?

The database, transaction programming and application programming are handled by the mainframe, and the terminal presents the user interface.

In regard to database relations, what is meant by the degree of a relation?

The degree of a relation is the number of attributes it contains.

What is a parent key?

The primary key referenced by a foreign key

David is designing a database to track tsunami activity worldwide. He is currently in the process of identifying valid primary keys for his tables. Which of the following should he keep in mind?

The primary key should be a value that will never change.

Consider the SQL statement in the exhibit. Which of the following is true? This

The statement creates a virtual table.

Ken has executed two CREATE TABLE statements, one for a table named Customers and one for a table named Orders. What can be said of these two tables?

The two tables are base tables.

What can be said about the two relations shown in the exhibit?

They are both strong entities.

Consider the following SQL statement: select addresses.c_num, a_address, c_first, c_last from addresses, customers where addresses.c_num = customers.c_num; What can be said of the addresses relation and the customers relation?

They both include a field named c_num.

Which of the following is true of primary keys and foreign keys?

They represent the data relationships within a relational database.

In a two-tier client-server architecture, what is the responsibility of the client system?

To present data to the user

What is the purpose of an entity-relationship (ER) model?

To provide a basic framework from which a database can be designed