Chapter 3-4 Flashcards
_____ expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
a) Relationship
b) Connectivity
c) Dependence
d) Cardinality
d) Cardinality
The entity relationship model uses the associative entity to represent a(n) _____ relationship between two or more entities.
a) M:N
b) N:1
c) 1:M
d) M:1
a) M:N
An entity in the entity relationship model corresponds to a table in the relational environment.
A) True
B) False
A) True
Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used.
A) True
B) False
A) True
The DIVIDE operation uses one single-column table (e.g., column “a”) as the divisor and one two-column table (e.g., columns “a” and “b”) as the dividend.
A) True
B) False
A) True
The SELECT operator yields a vertical subset of a table.
A) True
B) False
B) False
As rare as 1:1 relationships should be, certain conditions absolutely require their use.
A) True
B) False
A) True
In the entity relationship diagram (ERD), cardinality is indicated using the _____ notation, where max is the maximum number of associated entities and min represents the minimum number of associated entities.
a) (max, min)
b) (min, max)
c) [min … max]
d) {min|max}
b) (min, max)
Each table _____ represents an attribute.
a) column
b) row
c) value
d) dimension
a) column
_____ are especially useful when you are trying to determine what values in related tables cause referential integrity problems.
a) Equijoins
b) Inner joins
c) Outer joins
d) Theta joins
c) Outer joins
A(n) _____ is an orderly arrangement used to logically access rows in a table.
a) relationship
b) superkey
c) index
d) primary rule
c) index
According to Codd’s _____ rule of relational database, “Application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns).”
a) nonsubversion
b) integrity independence
c) logical data independence
d) comprehensive data sublanguage
c) logical data independence
A _____ is any key that uniquely identifies each row.
a) superkey
b) special key
c) candidate key
d) foreign key
a) superkey
The row’s range of permissible values is known as its domain.
A) True
B) False
B) False
The DIFFERENCE operator subtracts one table from the other.
A) True
B) False
A) True
A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.
A) True
B) False
B) False
Connectivities and cardinalities are established by concise statements known as business rules.
A) True
B) False
A) True
In the relational model, _____ are important because they are used to ensure that each row in a table is uniquely identifiable.
a) indexes
b) relations
c) logical structures
d) keys
d) keys
In Chen notation, there is no way to represent cardinality.
A) True
B) False
B) False
The _____ relationship should be rare in any relational database design.
a) M:1
b) 1:1
c) 1:M
d) M:N
b) 1:1
The idea of determination is unique to the database environment.
A) True
B) False
B) False
The entity relationship model (ERM) is dependent on the database type.
A) True
B) False
B) False
When using the Crow’s Foot notation, the associative entity is indicated by _____ relationship lines between the parents and the associative entity.
a) triple
b) double
c) dotted
d) solid
d) solid
When you define a table’s primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.
a) primary
b) key
c) composite
d) unique
d) unique
To implement a small database, a database designer must know the “1” and the “M” sides of each relationship and whether the relationships are mandatory or optional.
A) True
B) False
A) True
