Lesson 4 Flashcards
binary relationship
An ER term for an association (relationship) between two entities. For example, PROFESSOR teaches CLASS.
cardinality
A property that assigns a specific value to connectivity and expresses the range of allowed entity occurrences associated with a single occurrence of the related entity.
composite attribute
An attribute that can be further subdivided to yield additional attributes. For example, a phone number such as 615-898-2368 may be divided into an area code (615), an exchange number (898), and a four-digit code (2368). Compare to simple attribute
composite identifier
In ER modeling, a key composed of more than one attribute.
derived attribute
An attribute that does not physically exist within the entity and is derived via an algorithm. For example, the Age attribute might be derived by subtracting the birth date from the current date.
existence-dependent
A property of an entity whose existence depends on one or more other entities. In such an environment, the existence-independent table must be created and loaded first because the existence-dependent key cannot reference a table that does not yet exist.
existence-independent
A property of an entity that can exist apart from one or more related entities. Such a table must be created first when referencing an existence-dependent table.
identifiers
One or more attributes that uniquely identify each entity instance.
iterative process
A process based on repetition of steps and procedures.
mandatory participation
A relationship in which one entity occurrence must have a corresponding occurrence in another entity. For example, an EMPLOYEE works in a DIVISION. (A person cannot be an employee without being assigned to a company’s division.)
multivalued attributes
An attribute that can have many values for a single entity occurrence. For example, an EMP_DEGREE attribute might store the string “BBA, MBA, PHD” to indicate three different degrees held.
non-identifying relationship
A relationship in which the primary key of the related entity does not contain a primary key component of the parent entity.
optional attribute
In ER modeling, an attribute that does not require a value; therefore, it can be left empty.
optional participation
In ER modeling, a condition in which one entity occurrence does not require a corresponding entity occurrence in a particular relationship.
participants
An ER term for entities that participate in a relationship. For example, in the relationship “PROFESSOR teaches CLASS,” the teaches relationship is based on the participants PROFESSOR and CLASS.
recursive relationship
A relationship found within a single entity type. For example, an EMPLOYEE is married to an EMPLOYEE or a PART is a component of another PART.
relational schema
The organization of a relational database as described by the database administrator.
relationship degree
The number of entities or participants associated with a relationship. A relationship degree can be unary, binary, ternary, or higher.
required attribute
In ER modeling, an attribute that must have a value. In other words, it cannot be left empty.
simple attribute
An attribute that cannot be subdivided into meaningful components. Compare to composite attribute.
single-valued attribute
An attribute that can have only one value.
strong (identifying) relationship
A relationship that occurs when two entities are existence-dependent; from a database design perspective, this relationship exists whenever the primary key of the related entity contains the primary key of the parent entity.
strong entity
An entity that is existence-independent, that is, it can exist apart from all of its related entities. Also called a regular entity.
ternary relationship
An ER term used to describe an association (relationship) between three entities. For example, a DOCTOR prescribes a DRUG for a PATIENT.
unary relationship
An ER term used to describe an association within an entity. For example, an EMPLOYEE might manage another EMPLOYEE.
weak entity
An entity that displays existence dependence and inherits the primary key of its parent entity. For example, a DEPENDENT requires the existence of an EMPLOYEE.
weak relationship
A relationship in which the primary key of the related entity does not contain a primary key component of the parent entity.
The entity relationship model (ERM) is dependent on the database type. (T/F)
False
The Crow’s Foot notation is less implementation oriented than the Chen notation. (T/F)
False
An entity in the entity relationship model corresponds to a table in the relational environment.
True
In the entity relationship model, a table row corresponds to an entity instance. (T/F)
True
In the Chen and Crow’s Foot notations, an entity is represented with a rectangle containing the entity’s name. (T/F)
True
In the original Chen notation, each attribute is represented by an oval with the attribute name connected to an entity rectangle with a line. (T/F)
True
Software vendors have adopted the Chen representation because of its compact representation (T/F)
False
A composite identifier is a primary key composed of more than one attribute. (T/F)
True
The Crow’s Foot notation easily identifies multivalued attributes. (T/F)
False
Composite attributes make it easier to facilitate detailed queries. (T/F)
False
Relationships between entities always operate in one direction. (T/F)
False
Connectivities and cardinalities are established by concise statements known as business rules. (T/F)
True
In Chen notation, there is no way to represent cardinality. (T/F)
False
In implementation terms, an entity is existence-dependent if it has a mandatory primary key. (T/F)
False
A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity. (T/F)
False
In a 1:M relationship, to avoid the possibility of referential integrity errors, the data of the “1” side must be loaded first. (T/F)
True
Unary relationships are common in manufacturing industries. (T/F)
True
Referential integrity and participation are both bidirectional, meaning that they must be addressed in both directions along a relationship. (T/F)
False
A weak relationship, also known as a non-identifying relationship, exists if the primary key of the related entity does not contain a primary key component of the parent entity. (T/F)
True
The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity. (T/F)
False
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. (T/F)
True
The _____ notation of entity-relationship modelling can be used for both conceptual and implementation modelling.
UML
The entity relationship diagram (ERD) represents the _____ database as viewed by the end user.
conceptual
A(n) _____ is the set of possible values for a given attribute.
domain
Ideally, an entity identifier is composed of _____ attribute(s)
one
A _____ attribute can be further subdivided to yield additional attributes.
composite
A _____ attribute is one that cannot be subdivided.
simple
The conceptual model can handle _____ relationships and multivalued attributes.
M:N
A derived attribute is indicated in the Chen notation by a _____ that connects the attribute and an entity.
dashed line
The __________ attribute need not be physically stored within the database.
derived
A relationship is an association between _____.
Entities
_____ expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
cardinality
When the specific cardinalities are not included on the diagram in Crow’s Foot notation, cardinality is implied by the use of _____.
symbols
Knowing the minimum and maximum number of _____ occurrences is very helpful at the application software level.
entity
An entity is said to be _____ -dependent if it can exist in the database only when it is associated with another related entity occurrence.
existance
If an entity can exist apart from all of its related entities, then it is existence-independent, and it is referred to as a(n) _____ entity.
strong
A _____ entity does not have sufficient attributes to form a primary key.
weak
The existence of a(n) _____ entity indicates that its minimum cardinality is zero.
optional
The Crow’s foot symbol with two vertical parallel lines indicates _____ cardinality.
(1,1)
A _____ relationship exists when an association is maintained within a single entity.
unary
A _____ relationship exists when three entities are associated
ternary
If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a _____ relationship.
recursive
To simplify the conceptual design, most higher-order relationships are decomposed into appropriate equivalent _____ relationships whenever possible.
binary
The entity relationship model uses the associative entity to represent a(n) _____ relationship between two or more entities.
M:N
When using the Crow’s Foot notation, the associative entity is indicated by _____ relationship lines between the parents and the associative entity.
solid
______ are charcteristics of entities
Attribute
A _____ attribute is an attribute that must have a value
required
______ are underlined in an ER diagram
Identifiers
A person’s Social Security number would be an example of a ______ ______ attribute.
Single valued
A ______ attribute need not be physically stored within the database.
derived
A _____ attribute is an attribute that can be further subdivided to yield additional attributes.
composite
When indicating cardinality, the first value represents the _____ number of associated entities
minimum
The concept of relationship strength is based on how the ______ ______ of a related entity is defined.
primary key
A ______ relationship is also known as an identifying relationship.
strong
The Crow’s Foot notation depicts the strong relationship with a(n) _____ line between the entities.
solid
A weak entity must be ______ dependent.
existence
The Chen notation identifies a weak entity by using a double-walled entity ________.
rectangle
Participation is _______ if one entity occurrence does not require a corresponding entity occurrence in a particular relationship.
optional
In Crow’s Foot notation, an optional relationship between entities is shown by drawing a small _____ _____ on the side of the optional entity.
small circle/circle (o)
________ expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
Cardinality
A relationship _______ indicates the number of entities or participants associated with a relationship.
degree/cardinality
The process of database design is a sequential process. (T/F)
False
The first step in building an entity-relationship diagram (ERD) is _____ .
creating a detailed narrative of the organization’s description of operations
If Tiny College has some departments that are classified as “research only” and do not offer courses, the COURSE entity of the college database would be _____ the DEPARTMENT entity.
optional to
An ______ process is based on repetition of processes and procedures.
iterative
Identifying the attributes of entities helps in the better understanding of ______ among entities.
relationships
In organizations that generate large number of transactions, _____ are often a top priority in database design.
high processing speeds
Complex _____ requirements may dictate data transformations, and they may expand the number of entities and attributes within the design.
information
________ not only helps database designers to stay on track during the design process, it also enables them to pick up the design thread when the time comes to modify the design.
Documentation
