DATABASE MANAGEMENT SYSTEMS EXAM 1
What are the 5 SQL built in functions? - Answers - COUNT
SUM
AVG
MIN
MAX
Entity - Answers - some identifieable thing that users want to track.
Relation - Answers - a two-dimensional table that has certain characteristics
Characteristics of a relation - 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" - Answers - Table
File
What are two words that can be used interchangably with "Attribute" - Answers -
Column
Field
What are two words that can be used interchangably with "Tuple" - Answers - Row
Record
Functional Dependency - 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? - 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 - Answers - a combination of one or more columns that is used to identify rows in a
relation.
, Composite key - Answers - a key that consists of two or more columns
Candidate key - Answers - a key that determines all of the other columns in a relation
Primary key - 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 - Answers - An artificial column added to a relation to serve as a primary
key.
Foreign key - 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 - Answers - a statement that limits the values of the
foreign key to those already existing as primary key values in the corresponding
relation.
Anomaly - Answers - something unusual, unexpected or abnormal.
bad things when we work with databases.
Modification Anomalies - Answers - Deletion anomaly
insertion anomaly
update anomaly
Normal form - 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 - Answers - a table that qualifies as a relation
2NF - Answers - all of its nonkey attributes are dependent on all the attributes of the
primary key
3NF - Answers - if it is in 2NF and has no determininants except the primary key
Boyce-Codd Normal Form (BCNF) - Answers - if every determinant is a candidate key.
What are the 5 SQL built in functions? - Answers - COUNT
SUM
AVG
MIN
MAX
Entity - Answers - some identifieable thing that users want to track.
Relation - Answers - a two-dimensional table that has certain characteristics
Characteristics of a relation - 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" - Answers - Table
File
What are two words that can be used interchangably with "Attribute" - Answers -
Column
Field
What are two words that can be used interchangably with "Tuple" - Answers - Row
Record
Functional Dependency - 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? - 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 - Answers - a combination of one or more columns that is used to identify rows in a
relation.
, Composite key - Answers - a key that consists of two or more columns
Candidate key - Answers - a key that determines all of the other columns in a relation
Primary key - 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 - Answers - An artificial column added to a relation to serve as a primary
key.
Foreign key - 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 - Answers - a statement that limits the values of the
foreign key to those already existing as primary key values in the corresponding
relation.
Anomaly - Answers - something unusual, unexpected or abnormal.
bad things when we work with databases.
Modification Anomalies - Answers - Deletion anomaly
insertion anomaly
update anomaly
Normal form - 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 - Answers - a table that qualifies as a relation
2NF - Answers - all of its nonkey attributes are dependent on all the attributes of the
primary key
3NF - Answers - if it is in 2NF and has no determininants except the primary key
Boyce-Codd Normal Form (BCNF) - Answers - if every determinant is a candidate key.
