CPSC 440 Exam 1
What is an associateive entity?
An entity that associates the instances of one or more entity types and contains attributes specific to the relationships.
What is a Partial Dependency?
one or more nonkey attributes are functionally dependent on part, but not all, of the primary key.
What is a composite key?
primary key that consists of more than one attribute
What is the Second Normal Form?
relation that contains no multivalued attributes and has nonkey attributes solely dependnet on the primary key but contains transitive dependencies.
What is Referential Integrity Constraint?
rule that states that each foreign key value must match a primary key value in the other relation.
Cardinality Constraint
specifies the number of instances of one entity that can be associated with each instance of another entity.
When did E. F. Codd develop the relational model?
1970s
Employee (zero or many) -- (one or many) Department Describe this relationship.
A department can have one or more than one employee.
What is a Unary relationship?
A relationship between the instances of a single entity type is called a(n) _____ relationship.
What is a Ternary relationship?
A simultaneous relationship among the instances of three entity types.
What is the determinant?
Attribute on the left-hand side of the arrow in a functional dependency.
In SQL, what is used to make table definitions?
CREATE TABLE _______
A rule that CANNOT be violated by database users is called a _______
Constraint
A person, place, an object, an event or concept about which the organization wishes to maintain data is called _____
Entity
T or F: A ternary relationship is equivalent to three binary relationships
False
A student can attend five classes, each with a different professor. Each professor has 30 students. The relationship of students ot professors is a ______ relationship.
Many-to-many
What is the Entity Integrity Rule?
No primary key attribute may be null
T or F: A cascading delete removes all records in other tables associated with the record to be deleted.
True
T or F: A data model is a graphical system used to caputre the nature and relationships among data.
True
T or F: A multivalued attribute may take on more than one value for a particular entity instance
True
T or F: A physical schema contains the specifications of how data from a conceptual schema are stored in a computer's secondary memory.
True
T or F: A relational database establishes the relationships between entities by means of a common field.
True
T or F: a single occurrence of an entity is called an entity instance
True
What is an identifying relationship?
a relationship between a weak entity type and its owner.
What is a composite attribute?
an attribute that can be broken down into smaller parts.
What is a derived attribute?
an attribute that can be calculated form related attribute values.
What is a required attribute?
an attribute that must have a value for every entity (or relationship) instance.
What is a weak entity?
an entity type whose existence depends on another entity type.
What is a Partial Nonkey Dependency?
between two or more nonkey attributes.
When a regular entity type contains a multivalued attribute, one must:....
create two new relations, one containing the multivalued attribute