Chapter 4 Flashcards by John Frederickson

A data dictionary contains metadata - data about date.

True

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Current relational database software generally provides only a system catalog (and not a data dictionary).

True

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As rare as 1:1 relationships should be, certain conditions absolutely require their use.

True

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____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.

Predicate

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The relational model’s creator, E.F. Codd, used the term relation as a synonym for _____.

Table

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Date attributes contain calendar dates stored in a special format known as the ____ date format.

Julian

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In the relational model, ____ are important because they are used to ensure that each row in a table is uniquely identifiable.

Keys

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The attribute B is ____ the attribute A if each value in column A determines one and only one value in column B.

Functionally Dependent On

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A ____ key is any key that uniquely identifies each row.

Superkey

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Controlled ____ makes a relational database work.

Redundancy

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A ____ key is defined as a key that is used strictly for data retrieval purposes.

Secondary

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All primary key entries are unique, and no part of a primary key may be ____.

Null

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____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.

SELECT

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The ____ constraint can be placed on a column to ensure that every row in the table has a value for that column.

Not null

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____ combines all rows from two tables, excluding duplicate rows.

UNION

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A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).

Natural

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In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____.

Null

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A ____ contains at least all of the attribute names and characteristics for each table in the system.

Data Dictionary

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In a database context, the word ____ indicates the use of the same attribute name to label different attributes.

Homonym

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The ____ relational type if the “relational model ideal.”

1:M

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Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includes - as foreign keys - at least the ____ keys of the tables that are to be linked.

Primary

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A(n) ____ is an ordered arrangement of keys and pointers.

Index

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Codd’s Rule of ____ state:
Application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original tables values (changing order of columns or inserting columns).

Logical Data Independence

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To make a new table using SQL, you would use the CREATE TABLE command with mandatory appropriate data types specified for each of the attributes in the table.

True

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To permanently delete a table (its structure's existence), including any and all data it may have populated within it, which would be the SQL DDL command to accomplish that:

DROP TABLE

The following single SQL command would actually define a structure and build a table, in this case for a table named COMPANY, within a relational database. Also, it would not create any data within the table, but would be ready for SQL statements to follow up with populating the table given that it is now implemented. Please assume syntax is correctly specified: CREATE TABLE Company ( Co_Code INTEGER NOT NULL UNIQUE, Co_Name VARCHAR(30) NOT NULL, Co_Contact VARCHAR(30) NOT NULL, Co_State CHAR(2) NOT NULL. Co_Start_Dt DATE, PRIMARY KEY (Co_Code) );

True

An ERM is dependent on the database type.

False

The word “entity” in the ER model corresponds to a table.

True

The ER diagram represents the conceptual database as viewed by the end user.

True

The ER model refers to a specific table row as an entity instance.

True

In both the Chen and Crow’s Foot models, an entity is represented with a rectangle containing the entity’s name.

True

Attributes are types of entities.

False

In the original Chen model, each attribute is represented using an oval with the attribute name connected to the entity with a line.

True

Software vendors have adopted the Chen representation because of its compact representation.

False

Attributes cannot share a domain.

False

In an ER diagram, primary keys are usually bolded.

False

Ideally, a primary key is composed of several attributes.

False

All attributes are either simple or composite.

True

All simple attributes are also single-valued.

False

In the Chen model, a multivalued attribute is connected to the owning entity with a double line.

True

Derived attributes are stored in a special database table.

False

A relationship is identified by a name that describes the relationship.

True

Cardinality expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.

True

Connectivities and cardinalities are established by business rules.

True

A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.

False

You should always load data from the 1 side of a 1:M relationship.

True

The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity.

False

Relationships operate only in one direction.

False

A recursive relationship is one in which a relationship can exist between occurrences of the same entity set

True

The ERD represents the ____ database as viewed by the end user.

Conceptual

Some ____ database modeling concepts can be expressed only using the Chen notation.

Conceptual

The set of possible values for an attribute is a ____.

Domain

In an ER diagram, primary keys are indicated by ____.

Underlining

Ideally, an entity identifier is composed of ____ attribute(s).

One

The ____ attribute(s) make up the primary key in the table definition: CLASS (CRS_CODE, CLASS_SECTION, CLASS_TIME, CLASS_ROOM, PROF_NUM)

CRS_CODE CLASS_SECTION -CRS_CODE and CLASS_SECTION There is no primary key

A ____ attribute can be further subdivided to yield additional attributes.

Composite

A ____ attribute is one that cannot be subdivided.

Simple

____ attributes can have many values.

Multivalued

Some attributes are classified as ____.

-simple complex defined grouped

Although the conceptual model can handle ____ relationhips and multivalued attribues, you should not implement them in the RDBMS.

1: 1 - M:N 1: M 1: N

A derived attribute ____.

must be stored physically within the database -need not be physically stored within the database has many values must be based on the value of three or more attributes

A derived attribute is indicated in the Chen model by a ____.

dashed line

A relationship is an association between ____.

entities

In the ERD, cardinality is indicated using the ____ notation.

(min,max)

Another word for existence-independent is ____.

strong

An entity is said to be ____-dependent if it can exist in the database only when it is associated with another related entity occurrence.

existence

When the PK of one entity does not contain the PK of a related entity, the relationship is ____.

weak

A ____ entity has a primary key that is partially or totally derived from the parent entity in the relationship.

weak

The term “____” is used to label any condition in which one or more optional relationships exist.

optionality

The Crow’s foot symbol with two parallel lines indicates ____ cardinality.

(1,1)

A ____ relationship exists when an association is maintained within a single entity.

unary

A ____ relationship exists when two entities are associated.

binary

____ relationships are most common.

binary

If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a ____ relationship.

recursive

A(n) ____ entity is composed of the primary keys of each of the entities to be connected.

associative

The following step occurs first in the process of building an ERD: ____.

Develop the initial ERD. -Create a detailed narrative of the organization’s description of operations. Identify the attributes and primary keys that adequately describe the entities. Identify the business rules based on the description of operations.

The M:N relationship between STUDENT and CLASS must be divided into two 1:M relationships through the use of the ENROLL entity; the ENROLL entity is ____.

weak

Complex ____ requirements may dictate data transformations, and they may expand the number of entities and attributes within the design.

information

If Tiny College had some departments that were classified as “research only,” they would not offer courses; therefore, the COURSE entity would be ____ to the DEPARTMENT entity.

optional

A ____ relationship exists when an association is maintained within a single entity.

unary

A ____ relationship exists when three entities are associated.

ternary

If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a ____ relationship.

recursive

The associative entity is also known as a ____ entity.

composite

If Tiny College had some departments that were classified as “research only,” they would not offer courses; therefore, the COURSE entity would be ____ to the DEPARTMENT entity.

optional

If the focus is on data-retrieval speed, you might also be forced to include ____ attributes in the design, which would not ordinarily be done.

derived

Which of the following is used to select partial table contents?

SELECT FROM BY ; LIST FROM BY ; -SELECT FROM WHERE ; LIST FROM WHERE ;

Which query will output the table contents when the value of V_CODE is not equal to 21344?

-SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE FROM PRODUCT WHERE V_CODE <> 21344; SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE FROM PRODUCT WHERE V_CODE <= 21344; SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE FROM PRODUCT WHERE V_CODE = 21344; SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE FROM PRODUCT WHERE V_CODE => 21344;

Which query will output the table contents when the value of the character field P_CODE is alphabetically less than 1558-QW1?

-SELECT P_CODE, P_DESCRIPT, P_QOH, P_MIN, P_PRICE FROM PRODUCT WHERE P_CODE

The following two SQL commands would create 2 tables and would also create a relationship between the two tables with referential integrity. These two table definitions would also mean the following: A Company can have many Products, a Product can only have one Company, and a Company specified within a product must match a Company by its Company ID, Co_Code. Please assume syntax is correctly specified: CREATE TABLE Company Co_Code INTEGER NOT NULL UNIQUE, Co_Name VARCHAR(30) NOT NULL, Co_Contact VARCHAR(30) NOT NULL, Co_State CHAR(2) NOT NULL. Co_Start_Dt DATE, PRIMARY KEY (Co_Code) ); CREATE TABLE Product P_Code VARCHAR(10) NOT NULL UNIQUE, P_Desc VARCHAR(30) NOT NULL, P_InDate Date NOT NULL, P_QOH Smallint NOT NULL. P_Price NUMBER(8,2), Co_Code INTEGER, PRIMARY KEY (P_Code), FOREIGN KEY (Co_Code) REFERENCES Company (Co_Code) ;

True

Which of the following INSERT commands would not execute, in the sequence given, not because of bad syntax, but because of a bad value specified. There have been no other INSERT commands given previously to the heretofore empty tables. CREATE TABLE Company Co_Code INTEGER NOT NULL UNIQUE, Co_Name VARCHAR(30) NOT NULL, Co_Contact VARCHAR(30) NOT NULL, Co_State CHAR(2) NOT NULL. Co_Start_Dt DATE, PRIMARY KEY (Co_Code) ); CREATE TABLE Product P_Code VARCHAR(10) NOT NULL UNIQUE, P_Desc VARCHAR(30) NOT NULL, P_InDate Date NOT NULL, P_QOH Smallint NOT NULL. P_Price NUMBER(8,2), Co_Code INTEGER, PRIMARY KEY (P_Code), FOREIGN KEY (Co_Code) REFERENCES Company (Co_Code) ;

INSERT INTO Company Values ( 31439, 'Leath and Sons', 'Ian Leath', 'Mi', '19-Jan-00' ); INSERT INTO Product Values ( '16T-LJB', 'Top-Line JunkBin', '29-Mar-18', 57, 99.49, 31439 ); -INSERT INTO Product Values ( '16T-LJBC', 'Top-Line JB Cover', '29-Mar-18', 57, 7.99, 31440 ); No issues, the 3 above INSERT commands all execute