Chapter 9 Designing Databases
relational database model...
....represents data as a set of related tables or relations
data type..
...is a coding scheme recognized by system software for representing organizational data
foreign key...
...is an attribute that appears as a nonprimary key attribute in one relation and as a primary key attribute (or part of a primary key) in another relation.
field is...
...the smallest unit of named application data recognized by system software.
a primary key...
..is an attribute whose value is unique across all occurrences of a relation.
For a binary many-to-many relationship existing between entity types A and B: a. a separate relation C is created; the primary key of relation C is a composite key consisting of the primary key for each of the two entities in the relationship. b. the primary keys of relation A becomes a foreign key of relation B. c. secondary keys are used to establish the relationship. d. place the primary key of either entity in the relation for the other entity or do this for both entities. e. none of the above
A
If an associative entity exists, then: a. a separate relation C is created; the primary key of relation C is a composite key consisting of the primary key for each of the two entities in the relationship. b. the primary keys of relation A and relation B become foreign keys in a new relation C. c. secondary keys are used to establish the relationship. d. place the primary key of either entity in the relation for the other entity or do this for both entities. e. none of the above should be done.
A
If order number serves as the primary key in the order relation and also appears as a nonkey attribute in the invoice relation, then order number is said to be a: a. foreign key. b. candidate key. c. pointer. d. relationship key. e. marker
A
The most common style for a logical database model is the: a. relational database model. b. hierarchical database model. c. network database model. d. object-oriented database model. e. hybrid database model.
A
The process of converting complex data structures into simple, stable data structures is referred to as: a. normalization. b. simplification. c. structuring. d. process modeling. e. relational conversion.
A
A binary one-to-many relationship in an E-R diagram is best represented by: a. the creation of a separate relation; the primary key of this new relation is a composite key consisting of the primary key for each of the two entities in the relationship. b. adding the primary key attribute (or attributes) of the entity on the one side of the relationship as a foreign key in the relation that is on the many side of the relationship. c. adding the primary key attribute (or attributes) of the entity on the many side of the relationship as a foreign key in the relation that is on the one side of the relationship. d. creating a relation with a composite primary key and nonkey attributes. e. none of the above.
B
A data model that represents data in the form of tables or relations is called a(n): a. hierarchical database model. b. network database model. c. relational database model. d. hybrid database model. e. object-oriented database model.
C
A named two-dimensional table of data is a(n): a. network. b. tree structure. c. relation. d. tuple. e. object
C
Which of the following is not a true statement regarding a relation? a. Each relation consists of a set of named columns and an arbitrary number of unnamed rows. b. Each column in a relation corresponds to an attribute of that relation. c. An entry at the intersection of each row and column has a single value. d. Each row in a relation corresponds to an attribute of that relation. e. The rows may be interchanged or stored in any sequence.
D
. For a binary one-to-one relationship between two entities A and B, the relationship is represented by: a. adding the primary key of A as a foreign key of B. b. adding the primary key of B as a foreign key of A. c. combining the two entities into one relation. d. creating a third relation to represent the relationship between the two entities. e. either a or b.
E
3. The network model is the most common style for a logical database model.
F
A null value is used to represent the zero digit in a relation.
F
A relation corresponds to a computer file.
F
Conceptual modeling is performed during systems design.
F
Designing the database for an Internet-based electronic commerce application differs significantly from the process followed when designing the database for other types of applications.
F
Each column in a relation corresponds to an entity type.
F
Referencing a relation, the sequence of columns cannot be interchanged without changing the meaning or use of the relation.
F
The selection of data-storage technologies is made during the systems implementation and operation phase
F
A default value is a value a field will assume unless an explicit value is entered for that field
T
Each row of a relation corresponds to a record that contains data values for an entity.
T
If for every valid value of A the value of B is determined by the value of A, then B is functionally dependent on A.
T
Normalization helps build a data model that is simple, not redundant, and requires minimum maintenance.
T
One of the purposes of logical and physical database design is to choose data-storage technologies that will efficiently, accurately, and securely process database activities.
T
The selection of the appropriate storage format for each attribute from the logical database model is made during physical database design.
T
Normalization...
is the process of converting complex data structures into simple, stable data structures
