Review

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Review 4 Chapter 7,8,11,13,14
1. a. Entity Type- a collection of entities
that share common properties or characteristics
b. Entity-Relationship Model- a logical
representation of the data for an organization or
for
a business area c. Entity
Instance- A single occurrence of an entity type
d. Attribute- a property or characteristic of
an entity type that is of interest to the
organization For relational
databases, an attribute is a named column of a
relation. e. Relationship Type- a
meaningful association between entity types
f. Identifier- an attribute or combination of
attributes that uniquely identifies individual
instances of an entity type g.
Multivalued Attribute- an attribute that may
take on more than one value for a given
entity instance h. Associative Entity-
an entity type that associates the instances of
one or more entity types and contains
attributes that are peculiar to the relationship
between those entity instances
i. Cardinality Constraint- specifies the number
of instances of one entity that can or must be
associated with each instance
of another entity j. Weak Entity- an entity
type whose existence depends on some other entity
type k. Identifying Relationship- the
relationship between a weak entity type and its
owner l. Derived Attribute- an attribute
whose values can be calculated from related
attribute venues m. Multivalued Attribute-
already defined above
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2. a. Stored vs. derived attribute A stored
attribute is an attribute that stands alone. It
doesnt come from any other existing
attributes. A derived attribute is made from
stored attributes. Therefore, derived attributes
depend on stored attributes to exist. b.
Entity type vs. Entity instance An entity
instance is kind of like a polaroid of a entity
type. It is basically how an entity type looks
at a certain point in time. An entity type is a
collection of entities that share common
properties. c. Simple attribute vs.
Composite attribute Simply stated, a composite
attribute can be broken down into more specific
component parts while simple attributes cant.
They are already broken down as far as they can
go. d. Entity type vs. Relationship
type Entity types are a collection of entities
that share common properties. A
relationship type is a combination of entity
types that are related. e. Strong entity
type vs. Weak entity type A strong entity type
can exist by itself or on its own. A weak entity
type is dependent on a strong entity in order to
exist. f. Degree vs. Cardinality The
degree is the number of entity types that
participate in a relationship. The
cardinality is basically the range of entities
in a relationship.
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6. Mandatory One
PERSON
Has
SSN
Optional One
Is_Married_To
PERSON
Mandatory Many
PATIENT HISTORY
PATIENT
Has
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Optional Many
EMPLOYEE
Is_Assigned_To
PROJECT
7. Weak Entity Type
SONG
Is_Stocked_As
TAPE
Song_Name
Copy_Number
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8. The degree of a relationship is the number
of entity types that participate in that
relationship. A. Unary Relationship
Ex One employee manages many employees,
and many employees are managed by one
employee.
EMPLOYEE
Manages
B. Binary Relationship Ex Many students
can have many courses, and many courses can have
many students.
Registers_For
STUDENT
COURSE
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C. Ternary Relationship Ex
WAREHOUSE
SUPPLY SCHEDULE
VENDOR
PART
9. A. Derived Attribute Ex A major league
baseball players batting average. The derived
attribute is the actual batting average.
It is derived by the amount of hits a player has
divided by how many at bats he has.
B. Multivalued Attribute Ex An entity named
STATS for a baseball player would be an example
of a multivalued attribute. Stats could
include ERA, RBI, On-Base , Walks, etc.
C. Composite Attribute Ex An entity named
ATHLETE could be broken down into Professional
and Amateur.
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10. A. Ternary Relationship Ex
TEMPERATURE
Weather Forecast
Weather Forecast
DATE
LOCATION
B. Unary Relationship Ex
Contain
PARTS
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Chapter 13
1. a. Supertype- a generic entity type that
has a relationship with one or more subtypes
b. Subtype- a subgrouping of the entities in
an entity type that is meaningful to the org. and
that shares common attributes or
relationships distinct from other subgroupings
c. Specialization- the process of defining
one or more subtypes of the supertype, and
forming supertype/subtype relationships
d. Business Rule- a statement that defines
or constrains some aspect of the business. It is
intended to assert business structure
or to control or influence the behavior of
the business. e. Term- a word or phrase
that has a specific meaning for the business
f. Fact- an association between two or more
terms g. Subtype Discriminator- an
attribute of the supertype whose values determine
the target subtype or supertype h.
Constraint Base- an organized collection of
rules, usually stored in a repository i.
Generalization- the process of defining a more
general entity type from a set of more
specialized entity types j. Disjoint
Rule- specifies that is an entity instance is a
member of one subtype, it cannot
simultaneously be a member of any other subtype
k. Overlap Rule- specifies that an entity
instance can simultaneously be a member of two
or more subtypes
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2. Supertype vs. Subtype A supertype can be
broken down further into subtypes. Subtypes,
however, cant be broken down anymore.
Subtypes come from supertype specialization.
Generalization vs. Specialization Generalizati
on is a bottom-up approach that companies use
when they have a lot of specifics and want to
make a broad generalization out of the specific
entities. Specialization is the opposite. It
is top-down occurs when an org. wants to get
entities more specific. Constrained
object vs. Constraining object The constraining
object is what causes there to to be a
constrained object. A constraining object is
the entity, attribute, or relationship that
influences the ability to perform an operation
on the constrained object. Disjoint Rule
vs. Overlap Rule Disjoint rule means that a
member of one subtype can never be a member of
another subtype. Overlap rule says that two
subtypes can overlap with each other.
Structural Constraint vs. Operational
Constraint Structural constraints are business
rules that define the structure of the org.
Operational constraints are business rules that
make up the operations of the org. Total
Specialization Rule vs. Partial Specialization
Rule TSR means that everything has to fall under
one of the defined subtypes. ( It cant be part
of the supertype.) PSR means that entities can
be part of the defined subtype as well as be
part of the supertype.
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8. A. Supertype/Subtype w/Disjoint Rule
Ex How an org. pays its employees is the
perfect example of the disjoint rule. Employees
are either known as hourlies, salaries, or
consultants. They cant be anything else.
That is how they get paid, and that is how the
company identifies them. B.
Supertype/Subtype w/Overlap Rule
Ex A parts company is a good example of the
overlap rule. Parts can either be purchased
or manufactured or BOTH.
Chapter 6
1. a. Determinant- the attribute on the
left-hand side of the arrow in a functional
dependency b. Functional Dependency- a
constraint between two attributes or two sets of
attributes c. Transitive Dependency- a
functional dependency between two or more nonkey
attributes d. Recursive Foreign Key- a
foreign key in a relation that references the
primary key values of that same relation
e. Normalization- the process of
decomposing relations with anomalies to produce
smaller, well-structured relations
f. Composite Key- a primary key that consists of
more than one attribute g. Relation- a
named, two-dimensional table of data h.
Normal Form- a state of a relation that results
from applying simple rules regarding
functional dependencies to that relation
i. Partial Functional Dependency- a functional
dependency in which one or more
nonkey attributes are functionally dependent
on part but not all of the primary key
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2. Normal Form vs. Normalization Normalizatio
n is the process of decomposing relations with
anomalies to produce smaller, well-structured
relations. Whereas, normal form is a state of a
relation that results from applying simple rules
regarding functional dependencies to that
relation. Candidate Key vs. Primary
Key A candidate key defines a particular row in
a relation. Whereas, a primary key defines each
row in every table. Functional Dependency
vs. Transitive Dependency A functional
dependency is a constraint between two attributes
or two sets of attributes. A transitive
dependency is a functional dependency between two
or more nonkey attributes. Composite Key
vs. Recursive Foreign Key A composite key is
simply a primary key that consists of more than
one attribute. A recursive foreign key is a
foreign key that references the primary key
values of that same relation.
Determinant vs. Candidate Key A determinant is
an attribute that deals with a functional
dependency. Whereas, a candidate key is an
identifier of specified rows. 6. A relation
that has no partial functional dependencies is in
Second normal form. A relation that has
no multivalued attributes is in First normal
form. A relation that has no transitive
dependencies is in Third normal form.
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8. A. Regular Entity Type- represented by
rectangles with a single line B. 1M
Relationship- represented by one line with a
crows foot at the end of one side C.
MN Relationship- represented by one line with a
crows foot at each end of the line D.
Supertype/Subtype Relationship- represented by
one or two lines side by side connected
to a subtype which is also a
rectangle E. Multivalued Attribute-
represented by a double oval F. Weak
Entity- identified by a rectangle with a double
line G. Composite Attribute- an oval
with more specific ovals connected to it