- The entity supertype contains common characteristics, and the entity subtypes each contain their own unique characteristics.
True
2. The ____ constraint specifies whether each entity supertype occurrence must also be a member of at least one subtype.
completeness
3. The relationships depicted within the specialization hierarchy are sometimes described in terms of “is-a” relationships.
True
4. Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
False
5. In addition to the normal behavior, the EER model also supports specialization ____ where a subtype can have multiple parents (supertypes).
lattice
6. A subtype contains attributes that are common to all of its supertypes.
False
7. ____ relationships occur when there are multiple relationship paths between related entities.
Redundant
8. Your boss needs you to show a specialization hierarchy that can reflect the relation between EMPLOYEES and its subtypes. What type of relationship do you need to show your boss?
1:1
9. In specialization hierarchies with multiple levels of supertype and subtypes, a lower-level subtype can inherit only a few of the attributes and relationships from its upper-level supertypes.
False
10. What is the best data type for a primary key?
numeric
11. What type of entity can have disjoint or overlapping entity subtypes.
supertype
12. What type of subtypes are subtypes that contain nonunique subsets of the supertype entity set?
Overlapping
13. What do you add to the supertype table for a disjoint condition?
subtype discriminator
14. Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype.
True
15. What type of line represents a partial completeness constraint?
single horizontal line under the circle
16. What is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype?
specialization
17. An entity cluster is a “virtual” entity type used to represent multiple entities and relationships in the ERD.
True
18. The function of the primary key is to describe an entity.
False
19. To model time-variant data, one must create a new entity in an M:N relationship with the original entity.
False
20. A design trap occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world.
True
21. In the enhanced-entity-relationship, what is the collection of entities in this set classified as?
class
22. If we are creating subtypes for a car dealership. Why would an accountant be a subtype of an employee?
because it is identifiable with employees and has unique attributes
23. When there is a discriminator of a weak entity how is the set specified?
using a dashed line
24. Within a specialization hierarchy, every subtype can have _____ supertype(s) to which it is directly related.
only one
25. What type of identifier relationship ensures that the dependent entity can exist only when it is related to the parent entity?
strong
26. When looking at a college structure and their use of entity clusters, what are three things that would be considered part of the offerings?
semester, course, classes
27. One important inheritance characteristic is that all entity subtypes inherit their _____ key attribute from their supertype.
primary
28. What would be considered part of the entity cluster for Location?
building, room
29. What is the general rule that is used when using entity clusters?
to avoid the display of attributes
30. What type of key can never be used as a search key?
surrogate key
31. Which of the following is a specialization hierarchy disjoint constraint scenario, in the case of partial completeness?
Subtype discriminator can be null.
32. Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?
Supertype has optional subtypes.
33. Which of the following is an entity cluster?
location
34. When should you use a composite primary key?
As identifiers of composite entities, in which each primary key combination is allowed only once in the M:N relationship
35. Which of the following is an example of a foreign key?
Its value can be deleted from the child table.
36. Which of the following is an example of a primary key?
Its constraint can be implicitly defined on the temporary tables.
37. Without the ______, the primary key inheritance rule changes.
key attributes
38. The result of a grouping operation on simple entities is called a(n) ______.
entity cluster
39. Which of the following is an example of entity clustering for a doctor?
Surgeon, therapist, pediatrician
40. _____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.
Generalization
41. The purpose of an entity _____ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.
cluster
42. An entity cluster is formed by combining multiple interrelated entities into _____.
a single abstract entity object
43. The most important characteristic of an entity is its _____ key, used to uniquely identify each entity instance.
primary
44. A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.
natural
45. If one exists, a data modeler uses a _____ as the primary key of the entity being modeled.
natural identifier
46. A _____ is a primary key created by a database designer to simplify the identification of entity instances.
surrogate key
47. Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the _____ relationship.
M:N
48. The “_____” characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls.
unique values
49. The “_____” characteristic of a primary key states that the selected primary key must not be composed of any attribute(s) that might be considered a violation.
security-compliant
50. According to the “preferably single-attribute” characteristic of a primary key, the primary key:
should have the minimum number of attributes possible.
51. The “_____” characteristic of a primary key states that the primary key should not have embedded semantic meaning.
nonintelligent
52. What is the benefit of the entity clustering?
Avoid the display of attributes to eliminate complications that result when the inheritance rules change
53. Which of the following can be null?
foreign key
54. How many entities can be represented in an entity cluster?
Multiple
55. The __ is used to develop an initial ERD that contains a few entities.
Data modeler
56. Which of the answers below is not the most important characteristic of an entity?
A foreign key
57. Which of the answers below is familiar to end users and forms part of their day-to-day business vocabulary?
A natural key
58. Which of the answers below can be used to implement relationships among entities?
A foreign key
59. An entity cluster is considered “virtual” or “_____” in the sense that it is not actually an entity in the final ERD.
abstract
60. What is used by a data modeler when using a natural identifier of the entity being modeled and assuming that the entity has a natural identifier?
primary key
61. What is the best way to manage unique values, since the database can use internal routines to implement a counter-style attribute that automatically increments values with the addition of each new row?
numeric
62. Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed _____ in the M:N relationship.
only once
63. What type of keys are useful as identifiers of weak entities, where the weak entity has a strong identifier relationship with the parent entity?
composite key
64. When having a weak entity in a strong identifying relationship with a parent entity, what is used to represent the data model as two separate entities?
real-world object
65. What type of key has the practical advantage in that it has no intrinsic meaning?
surrogate
66. When using a surrogate key, one must ensure that the candidate key of the entity in question performs properly through the use of what constraints?
unique index
67. Using a data modeling point of view, what data refers to data whose values change over time and for which there must be kept a history of the data changes?
time-variant
68. Let’s assume that college football has many divisions. With this, each division has many players and each division has many teams. Given these “incomplete” business rules. What type of relationship is division in with the players and team?
division is in a 1:m relationship with team and players
69. The main concern with redundant relationships is that they remain _____ across the model.
consistent
70. The surrogate key has __ meaning in the user’s environment.
No meaning
71. What occurs when you have one entity in two 1:M relationships to other entities, which then produces an association among the other entities that is not expressed in the model?
fan trap
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