Quiz 1 Flashcards
- Defined as a concisely written set of users’ requirements, and should be specified in as detailed and complete a form as possible?
Data Requirements (91/92)
- Requirements that are user operations or transactions that will be applied to the database and may include both retrievals and updates.
Functional Requirements (92)* Not specified in ER diagram
- This class of design is usually easier to communicate to non-technical users because it doesn’t contain implementation details.
Conceptual Design (93)
- This class of design is often referred to as the implementation data model.
Logical Design (93)
This class of design includes the internal storage structures, file organizations, indexes, and access paths.
Physical Design (93)
- What are the two types of existence for entities in the Entity Relationship (ER) model (give an example of each type)?
a. Physical existence, example: a snowboard (94)
b. Conceptual existence, example: a company (94)
- These become a major part of the data stored in the database and describe each entity.
Attributes (94/95)
Types: composite vs simple, derived vs store, key vs non-key
Single vs multi-valued
Complex attributes (ie address-phone)
- These types of attributes are helpful to model an address when the user needs to refer to each part of the address independently (i.e., state, city, zip code, etc…).
Composite Attributes (96) (opposite is atomic)
- How do we specify the type of attribute from question 8 on an entity relationship (ER) diagram?
Show the composite attribute extending from the entity, then show the simple attributes extending from the composite attribute (114)
- With these types of attributes, the value can be determined by one or many other related attributes, or entities.
Derived Attributes (97)
- How do we specify the type of attribute from question 10 on an entity relationship (ER) diagram?
Put the attribute inside of a DASHED OVAL (114)
- Give two cases in which we may use the special “NULL” value?
If the attribute does not exist (example, apt # for single family home), or if the attribute is uknown (example, unpublished salary for an NFL coach) (97)
- These types of attributes have distinct values for each given entity set of an entity type E.
Key Attributes (99)
Subclasses: composite key, partial key (weak entity attribute with dotted underline)
- How many such entity sets are there for an entity type E with N entity instances (please explain your answer)?
There are 2^N entity sets. An entity set is “The collection of all entities of a particular entity type in the database at any point in time” also known as an entity collection (98/99). For each instance, there are two options, is it in the current set or not. For 3 possible instances: is entity 1 included (y/n), is entity 2 included (y/n), and is entity 3 included (y/n) = 2x2x2 = 8.
- When an attribute of one entity type refers to another entity type, what generally exists?
Relationship (103)
- The following is defined as the number of participating entity types in a relationship type R.
Degree (104)
- When the same entity type participates more than once in a relationship type (in different roles), this is referred to as what kind of relationship?
Recursive or self-referencing (106)
- The general term for the combination of cardinality and participation constraints on a relationship type R.
Structural Constraints (109)
- How many possible cardinality ratios are there for binary relationships (list them)?
4: 1:1, 1:N, N:1, and M:N (107)
- This constraint specifies the minimum number of relationship instances that each entity can participate in and is sometimes called the minimum cardinality constraint?
Participation Constraint (108)
- What are the two types participation constraint from (explain what each type means regarding a relationship type R, and two participating entity types E and D)?
Total and Partial (108)
For total, the minimum amount is at least 1
for partial, the minimum is 0
- Regarding attributes on relationship types, which cardinality ratio (of a binary relationship R from question 20) prevents me from migrating to either participating entity type in the relationship type R?
M:N because the participating entity type cannot migrate to EITHER. In general the participating entity type cannot migrate to an N side.
- Entity types that don’t have key attributes of their own are referred to as what?
Weak entity type (100)
- How do we specify weak entity types on an entity relationship (ER) diagram?
Double box
- The type of relationship that relates the weak entity type to its owner entity type?
Identifying Relationship (114)
- How do we specify an identifying relationship on an entity relationship (ER) diagram?
Double diamond
What is true about the participation of a weak entity type in the relationship type from question 26? What sort of dependency does this indicate?
The entity is in total participation (109) *Eludes to existence dependency
- True or false, entity types in an entity relationship (ER) diagram should be plural?
FALSE
- True or false, attribute names in an entity relationship (ER) diagram should have their first letter capitalized?
TRUE
- This notation allows us to combine both cardinality and participation constraints into one.
(min, max) (126)
- Give an example of this notation where an entity type has total participation.
(1,N) or (1,1)
- The process of defining a set of subclasses of an entity type is referred to as what?
Specialization (141)
The process of defining a set of superclasses of an entity type is refered to as what?
Generalization
- What are the two constraints we must specify on a subclass / superclass relationship?
Disjointness and Completeness
