CS6400 - Exam 3 UPDATED Questions
and CORRECT Answers
logical (or conceptual) level - CORRECT ANSWER✔✔- how users interpret the relation
schemas and the meaning of their attributes
implementation (or physical storage) level - CORRECT ANSWER✔✔- how the tuples in a
base relation are stored and updated
bottom-up design methodology - CORRECT ANSWER✔✔- (also called design by
synthesis) considers the basic relationships among individual attributes as the starting point
and uses those to construct relation schemas
top-down design methodology - CORRECT ANSWER✔✔- (also called design by analysis)
starts with a number of groupings of attributes into relations that exist together naturally
measures to determine the quality of relation schema design - CORRECT ANSWER✔✔- ■
Making sure that the semantics of the attributes is clear in the schema
■ Reducing the redundant information in tuples
■ Reducing the NULL values in tuples
■ Disallowing the possibility of generating spurious tuples
semantics of a relation - CORRECT ANSWER✔✔- refers to its meaning resulting from the
interpretation of attribute values in a tuple
update anomalies - CORRECT ANSWER✔✔- can be classified into insertion anomalies,
deletion anomalies, and modification anomalies
Insertion Anomalies - CORRECT ANSWER✔✔- occur when users attempt to store an
attribute value in the system but they cannot because the value of another unnecessary but
required attribute is not known
,Deletion Anomalies - CORRECT ANSWER✔✔- occur when a value for one attribute that
users wish to keep is unexpectedly removed when a value for another attribute is deleted
Modification Anomalies - CORRECT ANSWER✔✔- occur when changes to multiple
instances of an entity (rows of a table) are needed to effect an update to a single value of an
attribute
Spurious tuples - CORRECT ANSWER✔✔- Tuples generated by joining two relations on
attributes that are not keys or foreign keys on these relations.
Waste of storage space - CORRECT ANSWER✔✔- due to NULLs and the difficulty of
performing selections, aggregation operations, and joins due to NULL values
A functional dependency (A->B) - CORRECT ANSWER✔✔- occurs when the attribute A
uniquely determines B. A = left-hand side, B=right-hand-side.
-is a property of the semantics or meaning of the attributes.
FD or f.d. - CORRECT ANSWER✔✔- abbreviation for functional dependency
Candidate Key - CORRECT ANSWER✔✔- An attribute, or combination of attributes, that
uniquely identifies a row in a relation.
legal relation states (or legal extensions) of R - CORRECT ANSWER✔✔- Relation
extensions r(R) that satisfy the functional dependency constraints
FD cannot be inferred automatically - CORRECT ANSWER✔✔- must be defined explicitly
by someone who knows the semantics of the attributes of R.
diagrammatic notation - CORRECT ANSWER✔✔- isplaying FDs: Each FD is displayed as
a horizontal
, Normalization of Data - CORRECT ANSWER✔✔- a process of analyzing the given relation
schemas based on their FDs and primary keys to achieve the desirable properties of (1)
minimizing redundancy and (2) minimizing the insertion, deletion, and update anomalies
Boyce-Codd Normal Form (BCNF) - CORRECT ANSWER✔✔- A special type of third
normal form (3NF) in which every determinant is a candidate key. A table in BCNF must be
in 3NF.
normal form test - CORRECT ANSWER✔✔- is decomposed into smaller relation schemas
that contain a subset of the attributes and meet the test that was otherwise not met by the
original relation.
nonadditive join - CORRECT ANSWER✔✔- or lossless join property, guarantees that the
spurious tuple generation problem does not occur
dependency preservation property - CORRECT ANSWER✔✔- ensures that each functional
dependency is represented in some individual relation resulting after decomposition
superkey - CORRECT ANSWER✔✔- any key that uniquely identifies each row
key - CORRECT ANSWER✔✔- of a relation schema R = {A1, A2, ... , An} is a set of
attributes S ⊆ R with the property that no two tuples t1 and t2 in any legal relation state r of R
will have t1[S] = t2[S].
Candidate Key - CORRECT ANSWER✔✔- An attribute, or combination of attributes, that
uniquely identifies a row in a relation.
primary key - CORRECT ANSWER✔✔- A field (or group of fields) that uniquely identifies
a given entity in a table
prime attribute - CORRECT ANSWER✔✔- A key attribute; that is, an attribute that is part of
a key or is the whole key.
nonprime attribute - CORRECT ANSWER✔✔- An attribute that is not part of a key.
and CORRECT Answers
logical (or conceptual) level - CORRECT ANSWER✔✔- how users interpret the relation
schemas and the meaning of their attributes
implementation (or physical storage) level - CORRECT ANSWER✔✔- how the tuples in a
base relation are stored and updated
bottom-up design methodology - CORRECT ANSWER✔✔- (also called design by
synthesis) considers the basic relationships among individual attributes as the starting point
and uses those to construct relation schemas
top-down design methodology - CORRECT ANSWER✔✔- (also called design by analysis)
starts with a number of groupings of attributes into relations that exist together naturally
measures to determine the quality of relation schema design - CORRECT ANSWER✔✔- ■
Making sure that the semantics of the attributes is clear in the schema
■ Reducing the redundant information in tuples
■ Reducing the NULL values in tuples
■ Disallowing the possibility of generating spurious tuples
semantics of a relation - CORRECT ANSWER✔✔- refers to its meaning resulting from the
interpretation of attribute values in a tuple
update anomalies - CORRECT ANSWER✔✔- can be classified into insertion anomalies,
deletion anomalies, and modification anomalies
Insertion Anomalies - CORRECT ANSWER✔✔- occur when users attempt to store an
attribute value in the system but they cannot because the value of another unnecessary but
required attribute is not known
,Deletion Anomalies - CORRECT ANSWER✔✔- occur when a value for one attribute that
users wish to keep is unexpectedly removed when a value for another attribute is deleted
Modification Anomalies - CORRECT ANSWER✔✔- occur when changes to multiple
instances of an entity (rows of a table) are needed to effect an update to a single value of an
attribute
Spurious tuples - CORRECT ANSWER✔✔- Tuples generated by joining two relations on
attributes that are not keys or foreign keys on these relations.
Waste of storage space - CORRECT ANSWER✔✔- due to NULLs and the difficulty of
performing selections, aggregation operations, and joins due to NULL values
A functional dependency (A->B) - CORRECT ANSWER✔✔- occurs when the attribute A
uniquely determines B. A = left-hand side, B=right-hand-side.
-is a property of the semantics or meaning of the attributes.
FD or f.d. - CORRECT ANSWER✔✔- abbreviation for functional dependency
Candidate Key - CORRECT ANSWER✔✔- An attribute, or combination of attributes, that
uniquely identifies a row in a relation.
legal relation states (or legal extensions) of R - CORRECT ANSWER✔✔- Relation
extensions r(R) that satisfy the functional dependency constraints
FD cannot be inferred automatically - CORRECT ANSWER✔✔- must be defined explicitly
by someone who knows the semantics of the attributes of R.
diagrammatic notation - CORRECT ANSWER✔✔- isplaying FDs: Each FD is displayed as
a horizontal
, Normalization of Data - CORRECT ANSWER✔✔- a process of analyzing the given relation
schemas based on their FDs and primary keys to achieve the desirable properties of (1)
minimizing redundancy and (2) minimizing the insertion, deletion, and update anomalies
Boyce-Codd Normal Form (BCNF) - CORRECT ANSWER✔✔- A special type of third
normal form (3NF) in which every determinant is a candidate key. A table in BCNF must be
in 3NF.
normal form test - CORRECT ANSWER✔✔- is decomposed into smaller relation schemas
that contain a subset of the attributes and meet the test that was otherwise not met by the
original relation.
nonadditive join - CORRECT ANSWER✔✔- or lossless join property, guarantees that the
spurious tuple generation problem does not occur
dependency preservation property - CORRECT ANSWER✔✔- ensures that each functional
dependency is represented in some individual relation resulting after decomposition
superkey - CORRECT ANSWER✔✔- any key that uniquely identifies each row
key - CORRECT ANSWER✔✔- of a relation schema R = {A1, A2, ... , An} is a set of
attributes S ⊆ R with the property that no two tuples t1 and t2 in any legal relation state r of R
will have t1[S] = t2[S].
Candidate Key - CORRECT ANSWER✔✔- An attribute, or combination of attributes, that
uniquely identifies a row in a relation.
primary key - CORRECT ANSWER✔✔- A field (or group of fields) that uniquely identifies
a given entity in a table
prime attribute - CORRECT ANSWER✔✔- A key attribute; that is, an attribute that is part of
a key or is the whole key.
nonprime attribute - CORRECT ANSWER✔✔- An attribute that is not part of a key.
