Database Quizzes/Exams

Nulls are acceptable in a primary key field T/F

False

Primary keys and foreign keys are the same (T/F)

False

Multivalued attribute

An attribute for which instances of an entity can have multiple values for the same attribute. (Employee could have multiple phone numbers)

Problems with Data Dependency

Duplication of data, Limited data sharing, Lengthy Development Times, Excessive program maintenance

Properties of relations

Each attribute has a unique name No two rows in a relation are identical There are no multivalued attributes in a relation

In order for a table to be a relation, the following conditions must hold:

Each column must have a name Within one table, each row must be unique Within each row, each value in each column must be single valued All values in each column must be from the same (predefined) domain Order of columns is irrelevant Order of rows is irrelevant

A Database contains

End-user data: raw facts of interest to end user Metadata: data about data and provides a description of data characteristics and relationship in the data.

The first popular use of a database, SABRE for airlines, also led to the first ethical issue in database use (T/F)

True

There are two broad categories of databases, OLTP (transaction databases) and OLAP (data warehouses) (T/F)

True

Metadata

data about data, schema

Data dependence

data access changes with data storage characteristics change

Physical database design decisions must be made carefully because of impacts on

data accessibility, response times, security

Program-data dependence is caused by

data descriptions being written into programming code

Another form of denormalization where the same data are stored in multiple places in the database are called..

data duplication

User-defined constraints

database constraints that are added by the database designer

An attribute that can be calculated from related attribute values is called a(n)..

derived attribute

Data

facts that are recorded and can be accessed, raw numbers and facts

Data management

focuses on proper generation, storage, and retrieval of data

Referential integrity constraint

in each row of a relation containing a foreign key, the value of the foreign key either matches one of the values in the primary key column of the referred relation or the value of the foreign key is null.

___________ are used to query data from two or more tables, based on a relationship between some columns in the tables

joins

Relational database model

logical database model that represents a database as a collection of related tables

A student can attend 5 classes, each with a different professor. Each professor has 30 students. The relationship of students to professors is a

many-to-many relationship

Transforming the data specifications into basic, or atomic elements following well-established rules is called..

normalization

Unary relationship (recursive relationship)

occurs when an entity is involved in a relationship with itself (degree 1 relationship)

An attribute or attributes that uniquely identifies each row in a relation is called a..

primary key

Not an advantage of database systems

redundant data

Information

refers to the data that is accessed by a user for some particular purpose, the result of processing raw data to reveal meaning

Degree of a relationship

reflects how many entities are involved in the relationship

A two-dimensional table of data is called a..

relation

Binary relationship

relationship between two entities

A business rule specification should be..

simple and well structured

A simultaneous relationship among the instances of three entity types is called a(n)

ternary relationship

Implicit constraint

the implicit relational database model rules that a relational database must satisfy in order to be valid

Primary keys

unique identifiers that can be used to retrieve a single row from the table

Relational schema

visual depiction of the relational database model, a picture of the database

Data that describes the properties and context of the user data is known as

Meta-data

A candidate key must satisfy all of the following conditions

The key must uniquely identify the row The key must be nonredundant Each nonkey attribute is functionally dependent upon it

A business rule is a statement that defines or constrains some aspect of the business T/F

True

A primary key is an attribute that uniquely identifies each row in a relation T/F

True

A table must be in first normal form (1NF) before it can be in second normal form (2NF) (T/F)

True

An entity can have more than one unique attribute. In such cases each unique attribute is also called a candidate key (T/F)

True

By adding a check constraint to a table as it is being created, DBAs can control the values are entered into a given field (T/F)

True

Databases need to contain, not only the data, but also indexes, statistics, privileges, stored procedures, etc. T/F

True

Development starts from scratch with the traditional file processing approach because new file formats, descriptions, and file access logic must be designed for each new program T/F

True

Enforcement of business rules can be automated through the use of software tools that can interpret the rules and enforce them T/F

True

Hierarchial and Network were two database models that were used early on, but were not used much more (T/F)

True

Information is processed data T/F

True

It is recommended that every table have a primary key (T/F)

True

Metadata are data that describe the properties of other data T/F

True

Relational databases view all data in the form of tables T/F

True

Multiple unique attributes (candidate keys)

When an entity has more than one unique attribute each unique attribute is also called a candidate key (Employee ID and SSN could have key fields)

The SQL command ___________ defines a logical table from one or more tables or views

create view

Data independence

data storage characteristics do not affect data access

An attribute in a relation of a database that serves as the primary key of another relation in the same database is called a

foreign key

Not a cost and/or risk of the database approach

improved responsiveness

Entity Integrity Constraint

in a relational table, no primary key column can have null or empty values

Normalization

is the process of organizing data in a database, includes establishing relationships between tables according to rules designed both to protect the data and to make the database more flexible by eliminating redundancy and inconsistent dependency

The definition of the database that provides all the specifications to a specific database management system is contained in a(n)..

physical schema

Database Management System

A software system that is used to create, maintain, and provide controlled access to user databases. Manages data resources like an operating system manages hardware resources

Database

A structured collection of records or data that is stored in a computer

Relation

A table in a relational database A table containing rows and columns The main construct in the relational database model Every relation is a table, not every table is a relation

First Normal Form

Every column must contain only a single value No table can have repeating groups of data No multi-valued attributes Every attribute value is dependent on everything else

A constraint is a rule in a database system that can be violated by users T/F

False

All databases available today are Relational databases (T/F)

False

Conceptual database designs are closely tied to the brand of database an organization is using (T/F)

False

DBAs decide for the company what the business rules are and implement them in the database (T/F)

False

Data and Information are the same (T/F)

False

Databases can be in a second normal form without being in first normal form T/F

False

Databases that are highly normalized will always give the best performance T/F

False

The terms "database" and "database management system (DBMS)" refer to the same thing (T/F)

False

Unlike columns, the rows of a relation may not be interchanged and must be stored in one sequence T/F

False

A column in a relation that refers to a primary key column in another (referred) relation is called a

Foreign Key

E.F. Codd developed the relational model of the..

1970s

Second Normal Form

1NF plus every non-key attribute is fully functionally dependent on the entire primary key

Third Normal Form

2Nf plus no transitive dependencies (functional dependencies on non-primary-key attributes)

The following criteria should be considered when selecting an identifier..

Choose an identifier that is stable Choose an identifier that won't be null Choose an identifier that doesn't have large composite attributes

Business rules govern the validity of data T/F

True

Relational database

a collection of related relations within which each relation has a unique name

Ternary relationship

a relationship involving three entities (deree 3 relationship)

Relationship roles

additional syntax that can be used in ER diagrams that the discretion of a data modeler to clarify the role of each entity in a relationship

Program Data dependency

All programs maintain metadata for each file they use

Optional attribute

An attribute that is allowed to not have a value (can be null)

Composite unique attribute

An attribute that is composed of several attributes and whose value is different for each entity instance

Composite Attribute

An attribute that is composed of several attributes. Its purpose is to indicate a situation in which a collection of attributes has an additional meaning, besides the individual meanings of each attribute.

The benefits of a standardized relational language include:

Application longevity Reduced training costs Cross-system communication Potential portability of applications

The following is an objective of selecting a data type

Represent a small number of possible values Maximize storage space Limit security

A primary key that consists of more than one attribute is called a..

composite key

In the SQL language the _____________ statement is used to make table definitions

create table