CIS 3050 CH 5

___________________means that not every supertype occurrence is a member of a subtype; some subtype occurrences may not be members of any subtype. a. Partial completeness b. Partial subtypes c. Disjoint subtypes d. Specialization subtypes

a. Partial completeness

___________________means that every supertype occurrence must be a member of at least one subtype. a. Total completeness b. Total subtypes c. Specialization subtypes d. Partial completeness

a. Total completeness

A(n) _______________ occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world. a. design trap b. derived attribute c. dangling entity d. fan trap

a. design trap

A(n) ________________ is the attribute in the supertype entity that is used to determine to which entity subtype the supertype occurrence is related. a. subtype discriminator b. overlapping supertype c. specialization hierarchy d. disjoint supertype

a. subtype discriminator

A(n) ___________________ key is a primary key created by the database designer to simplify the identification of entity instances and it has no meaning in the user's environment (i.e., it only exists to distinguish one entity instance from another). a. surrogate b. candidate c. foreign d. composite

a. surrogate

What symbol is used on a diagram to represent a disjoint , or nonoverlapping, subtype? a. A circle with an 'o' in it that is placed between the supertype and subtype b. A circle with a 'd' in it that is placed between the supertype and subtype c. A double horizontal line that is placed between the supertype and subtype d. An empty circle that is placed between the supertype and subtype

b. A circle with a 'd' in it that is placed between the supertype and subtype

What would have to appear in the data model in order for every entity instance in a supertype PRODUCT entity to be associated with an entity instance in the subtype CD entity? a. A single subtype discriminator would need to be present in the supertype PRODUCT that is set to 'CD'. b. A discriminator attribute for the CD entity would need to be present in the supertype PRODUCT entity that is set to '1' or 'TRUE'. c. The total completeness constraint would need to be set on the subtype CD entity only. d. None of these choices are correct.

b. A discriminator attribute for the CD entity would need to be present in the supertype PRODUCT entity that is set to '1' or 'TRUE'.

Which of the following is NOT considered a desirable characteristic of a primary key? a. It should be a single attribute or the minimum number of attributes possible b. It should change over time c. Nonintelligent or no embedded semantic meaning d. It should be numeric

b. It should change over time

If there exists a supertype entity called PRODUCT and a subtype entity below it called BOOK, is it possible for a book to appear in the BOOK table without appearing in the PRODUCT table? a. Yes, if total completeness exists between the supertype and subtype. b. No, subtypes can only exist within the context of a supertype. c. Yes, if partial completeness exists between the supertype and subtype. d. Yes, it is possible for a subtype to exist without it being present in a supertype.

b. No, subtypes can only exist within the context of a supertype

A(n) ________________is based on the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype and is based on grouping unique characteristics and relationships of the subtypes. a. subtype discriminator b. specialization hierarchy c. overlapping supertype d. disjoint supertype

b. specialization hierarchy

Under what circumstances are composite primary keys appropriate? a. as identifiers of weak entities, where the weak entity has a strong identifying relationship with the parent entity b. as identifiers of composite entities, where each primary key combination is allowed only once in the M:N relationship c. All of these choices are correct. d. None of these choices are correct.

c. All of these choices are correct.

What kinds of data would you store in an entity supertype versus an entity subtype? a. The entity supertype contains the common characteristics b. The entity subtypes contain the unique characteristics of each entity subtype c. All of these choices are correct. d. None of these choices are correct.

c. All of these choices are correct.

___________________are subtypes that contain non-unique subsets of the supertype entity set; that is, each entity instance of the supertype may appear in more than one subtype. a. Disjoint subtypes b. Specialization subtypes c. Overlapping subtypes d. Discriminator subtypes

c. Overlapping subtypes

When implementing a 1:1 relationship, where should you place the foreign key if one side is mandatory and one side is optional and should the foreign key be mandatory or optional? a. Select the FK that causes the fewest number of nulls or place the FK in the entity in which the (relationship) role is played. b. Revise your model to ensure that the two entities do not belong together in a single entity. c. Place the PK of the entity on the mandatory side in the entity on the optional side as a FK and make the FK mandatory. d. None of these choices are correct.

c. Place the PK of the entity on the mandatory side in the entity on the optional side as a FK and make the FK mandatory.

If a supertype entity called PRODUCT has attributes of Prod_Num, Prod_Title, Prod_ReleaseDate, Prod_Price, and Prod_type and a subtype entity called MOVIE has attributes of Prod_Num, Movie_Rating, Movie_Director, and a subtype entity called CD has attributes of Prod_Num, CD_Genre, and CD_Artist, what are considered the attributes of a movie? a. Prod_Num, Movie_Rating, Movie_Director b. Prod_Num, Movie_Rating, Movie_Director , CD_Genre, and CD_Artist c. Prod_Num, Prod_Title, Prod_ReleaseDate, Prod_Price, Prod_type, Movie_Rating, Movie_Director d. All of these attributes are listed in the question.

c. Prod_Num, Prod_Title, Prod_ReleaseDate, Prod_Price, Prod_type, Movie_Rating, Movie_Director

How does one implement overlapping subtypes in a ER diagram? a. Use a special color on the diagram b. Use a circle with an 'o' in it between the supertype and subtype c. Use a separate discriminator attribute for each subtype in the supertype entity d. Use a single subtype discriminator in the supertype entity

c. Use a separate discriminator attribute for each subtype in the supertype entity

A _____is an entity set or child entity that contains unique characteristics or attributes within a more broadly defined parent entity . a. supertype b. relationship c. subtype d. surrogate

c. subtype

Which of the following is the primary reason for using entity supertypes? a. To make the ER diagram more readable b. To maximize the number of nulls and to increase the likelihood of redundant relationships c. To please the end-users with state-of-the-art designs d. To minimize the number of nulls and to minimize the likelihood of redundant relationships

d. To minimize the number of nulls and to minimize the likelihood of redundant relationships

A _____is an entity set that contains the commonly shared characteristics of it entities or subtypes. It includes characteristics that are not common to all entities within the set and becomes the parent to one or more subtypes in the hierarchy. a. surrogate b. relationship c. subtype d. supertype

d. supertype

In the data modeling point of view, ________________________ data refer to data whose values change over time and for which you must keep a history of the data changes. a. location-specific b. surrogate c. static d. time-variant

d. time-variant