Database Management Systems Exam 1(Correct
answers)
What are the 5 SQL built in functions? correct answers COUNT
SUM
AVG
MIN
MAX
Entity correct answers some identifieable thing that users want to track.
Relation correct answers a two-dimensional table that has certain characteristics
Characteristics of a relation correct answers - each relation in a database has a unique name
- rows contain data about a specific instance of an entity
- columns contain data about attributes of the entity class
- all entries in a column are of the same kind
- each column in a given table has a unique name
- cells of the table hold a single value
- the order of the columns is unimportant
- the order of the rows is unimportant
- no two rows may be identical
What are two words that can be used interchangably with "Relation" correct answers Table
File
What are two words that can be used interchangably with "Attribute" correct answers Column
Field
What are two words that can be used interchangably with "Tuple" correct answers Row
Record
Functional Dependency correct answers occurs when the value of one (set of) attribute(s)
determines the value of a second (set of) attribute(s)
if A > (B,C) then A > B and A > C
if (A,B) > C then neither A nor B determines C by itself
What makes a determinant value unique? correct answers a determinant is unique in a relation if
and only if, it determines every other column in the relation.
You cannot find the determinant of all functional dependencies simply by looking for unique
values in one column
Key correct answers a combination of one or more columns that is used to identify rows in a
relation.
, Composite key correct answers a key that consists of two or more columns
Candidate key correct answers a key that determines all of the other columns in a relation
Primary key correct answers a candidate key selected as the primary means of identifying rows
in a relation.
There is ony one primary key per relation.
The primary key may may be a composite key
the ideal pimary key is short, numeric, and never changes.
Surrogate key correct answers An artificial column added to a relation to serve as a primary key.
Foreign key correct answers the primary key of one relation that is placed in another relation to
form a link between the relations.
can be a single column or a compostie key.
the term refers to the fact that key values are foreign to the relation in which they appear as
foreign key values.
referenctial integrity constraint correct answers a statement that limits the values of the foreign
key to those already existing as primary key values in the corresponding relation.
Anomaly correct answers something unusual, unexpected or abnormal.
bad things when we work with databases.
Modification Anomalies correct answers Deletion anomaly
insertion anomaly
update anomaly
Normal form correct answers a relation is in normal form if it conforms to a defined set of rules
(norms)
a relation that conforms to the x set of rules is said to be in xNF.
The purpose is to help us prevent anomalies.
1NF correct answers a table that qualifies as a relation
2NF correct answers all of its nonkey attributes are dependent on all the attributes of the primary
key
3NF correct answers if it is in 2NF and has no determininants except the primary key
Boyce-Codd Normal Form (BCNF) correct answers if every determinant is a candidate key.
Process for putting relations into BCNF correct answers 1. identify every functional dependency
2. identify every candidate key
3. if there is a functional dependency that has a determinant that is not a candidate key
a. move the columns of that functional dependency into a new relation
answers)
What are the 5 SQL built in functions? correct answers COUNT
SUM
AVG
MIN
MAX
Entity correct answers some identifieable thing that users want to track.
Relation correct answers a two-dimensional table that has certain characteristics
Characteristics of a relation correct answers - each relation in a database has a unique name
- rows contain data about a specific instance of an entity
- columns contain data about attributes of the entity class
- all entries in a column are of the same kind
- each column in a given table has a unique name
- cells of the table hold a single value
- the order of the columns is unimportant
- the order of the rows is unimportant
- no two rows may be identical
What are two words that can be used interchangably with "Relation" correct answers Table
File
What are two words that can be used interchangably with "Attribute" correct answers Column
Field
What are two words that can be used interchangably with "Tuple" correct answers Row
Record
Functional Dependency correct answers occurs when the value of one (set of) attribute(s)
determines the value of a second (set of) attribute(s)
if A > (B,C) then A > B and A > C
if (A,B) > C then neither A nor B determines C by itself
What makes a determinant value unique? correct answers a determinant is unique in a relation if
and only if, it determines every other column in the relation.
You cannot find the determinant of all functional dependencies simply by looking for unique
values in one column
Key correct answers a combination of one or more columns that is used to identify rows in a
relation.
, Composite key correct answers a key that consists of two or more columns
Candidate key correct answers a key that determines all of the other columns in a relation
Primary key correct answers a candidate key selected as the primary means of identifying rows
in a relation.
There is ony one primary key per relation.
The primary key may may be a composite key
the ideal pimary key is short, numeric, and never changes.
Surrogate key correct answers An artificial column added to a relation to serve as a primary key.
Foreign key correct answers the primary key of one relation that is placed in another relation to
form a link between the relations.
can be a single column or a compostie key.
the term refers to the fact that key values are foreign to the relation in which they appear as
foreign key values.
referenctial integrity constraint correct answers a statement that limits the values of the foreign
key to those already existing as primary key values in the corresponding relation.
Anomaly correct answers something unusual, unexpected or abnormal.
bad things when we work with databases.
Modification Anomalies correct answers Deletion anomaly
insertion anomaly
update anomaly
Normal form correct answers a relation is in normal form if it conforms to a defined set of rules
(norms)
a relation that conforms to the x set of rules is said to be in xNF.
The purpose is to help us prevent anomalies.
1NF correct answers a table that qualifies as a relation
2NF correct answers all of its nonkey attributes are dependent on all the attributes of the primary
key
3NF correct answers if it is in 2NF and has no determininants except the primary key
Boyce-Codd Normal Form (BCNF) correct answers if every determinant is a candidate key.
Process for putting relations into BCNF correct answers 1. identify every functional dependency
2. identify every candidate key
3. if there is a functional dependency that has a determinant that is not a candidate key
a. move the columns of that functional dependency into a new relation
