logo image

Ch 3-6

_____ relationships can be implemented by creating a new entity in 1:M relationships with the original entities.
The DIFFERENCE operator subtracts one table from the other
In a natural join, the column on which the join was made occurs twice in the new table.
A _____ is any key that uniquely identifies each row.
The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents
system catalog
The order of the rows and columns is important to the DBMS
The ____ relationship should be rare in any relational database design
Only a single attribute, not multiple attributes, can define functional dependence
If the attribute (B) is functionally dependent on a composite key (A) but not on any subset of that composite key, the attribute (B) is fully functionally dependent on (A).
You can think of a table as a persistent representation of a logical relation.
A null is created when you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind.
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.
Referential _____ dictates that the foreign key must contain values that match the primary key in the related table, or must contain null.
RDBMSs enforce integrity rules automatically.
A relationship is an association between _____.
Relationships between entities always operate in one direction
A ____ attribute is one that cannot be subdivided
When the specific cardinalities are not included on the diagram in Crow’s Foot notation, cardinality is implied by the use of _____.
The entity relationship model uses the associative entity to represent a(n) _____ relationship between two or more entities.
An entity is said to be _____-dependent if it can exist in the database only when it is associated with another related entity occurrence.
The Crow’s foot symbol with two vertical parallel lines indicates ___ cardinality.
A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.
Ideally, an entity identifier is composed of ___ attribute(s)
Connectivities and cardinalities are established by concise statements known as business rules.
In the Chen and Crow’s Foot notations, an entity is represented with a rectangle containing the entity’s name.
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.
(min, max)
In a 1:M relationship, to avoid the possibility of referential integrity errors, the data of the “1” side must be loaded first.
Nonoverlapping subtypes are subtypes that contain a(n) _____ subset of the supertype entity set.
Generalization is based on grouping unique characteristics and relationships of the subtypes.
A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.
The most important characteristic of an entity is its _____ key, used to uniquely identify each entity instance.
The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.
Some designs use redundant relationships as a way to simplify the design.
A subtype contains attributes that are common to all of its supertypes
One important inheritance characteristic is that all entity subtypes inherit their _____ key attribute from their supertype.
Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.
At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a 1:1 relationship.
Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?
Supertype has optional subtypes
If one exists, a data modeler uses a _____ as the primary key of the entity being modeled.
natural identifier
In specialization hierarchies with multiple levels of supertype and subtypes, a lower-level subtype can inherit only a few of the attributes and relationships from its upper-level supertypes.
Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.
Normalization represents a micro view of the entities within the ERD.
Normalization produces a lower normal form
Converting a database format from 1NF to 2NF is a complex process
A determinant is any attribute whose value determines other values within a column.
A(n) _____ exists when there are functional dependencies such that Y is functionally dependent on X, Z is functionally dependent on Y, and X is the primary key.
Transitive dependency
In the context of partial dependencies, data redundancies occur because every row entry requires duplication of data.
A table is in fourth normal form if it is in third normal form and has no independent multivalued dependencies.
Normalization is a very important database design ingredient, and the highest level is always the most desirable.
A _____ derives its name from the fact that a collection of multiple entries of the same type can exist for any single key attribute occurrence.
repeating group
1NF, 2NF, and 3NF are _____
normalization stages
Repeating groups must be eliminated by ensuring that each row defines a single entity.
Denormalization produces a lower normal form
The combination of normalization and ER modeling yields a useful ERD, whose entities can be translated into appropriate relationship structures.
If a table has multiple candidate keys and one of those candidate keys is a composite key, the table can have based on this composite candidate key even when the primary key chosen is a single attribute.
partial dependencies
To generate a surrogate key, Microsoft Access uses a(n) ____ data type.
Dependency diagrams are very helpful in getting a bird’s-eye view of all the relationships among a table’s attributes.
An attribute that is part of a key is known as a(n) ______ attribute.
From a structural point of view, 2NF is better than _____.
The CUSTOMER table’s primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of _____ integrity.
A _____ contains at least all of the attribute names and characteristics for each table in the system.
data dictionary
Another name for a composite entity is a(n) _____ entity
A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.
_____ are especially useful when you are trying to determine what values in related tables cause referential integrity problems.
Outer joins
When you define a table’s primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.
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).”
logical data independence
_____ databases reflect the ever-growing demand for greater scope and depth in the data on which decision support systems increasingly rely.
data warehouse
If you have 3 different transitive dependencies, ___ different determinant(s) exist.
Dependencies based on only a part of a composite primary key are known as _____ dependencies.
The “_____” characteristic of a primary key states that the selected primary key must not be composed of any attribute(s) that might be considered a violation.
The “_____” characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls.
unique values
Partial completeness constraint is represented by
a single horizontal line under a circle
According to the “preferably single-attribute” characteristic of a primary key, the primary key:
should have the minimum number of attributes possible
____ keys work with primary keys to properly implement relationships in the relational model
____ is a generic entity type that is related to one or more entity subtypes
An entity supertype
A primary key’s main function is to uniquely identify a(n) ___ within a table
entity instance or row
Complex _____ requirements may dictate data transformations, and they may expand the number of entities and attributes within the design.
The decision to store _____ attributes in database tables depends on the processing requirements and the constraints placed on a particular application.
A ____ attribute can be further subdivided to yield additional attributes.
A ____ entity has a primary key that is partially or totally derived from the parent entity in the relationship
The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity
Referential integrity and participation are both bidirectional, meaning that they must be addressed in both directions along a relationship.
The Crow’s Foot notation easily identifies multivalued attributes.
A ____ relationship exists when an association is maintained within a single entity
The ____ constraint can be placed on a column to ensure that every row in the table has a value for that column
Data attributes contain calendar dates stored in a specific format known as the ___ date format
The row’s range of permissible values is known as its domain.
A data dictionary is sometimes described as “the database designer’s database” because it records the design decisions about tables and their structures.
In the relational model, _____ are important because they are used to ensure that each row in a table is uniquely identifiable.
The one-to-many (1:M) relationship is easily implemented in the relational model by putting the foreign key of the “1” side in the table of the “many” side as a primary key.
To be considered minimally relational, the DBMS must support the key relational operators _____, PROJECT, and JOIN.
_____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.
Each table in a relational database must have a primary key.
Each table ____ represents an attribute
____ returns only the attributes requested, in the order in which they are requested.
_____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.
Character data can contain any character or symbol intended for mathematical manipulation.
A(n) _____ join links tables by selecting only the rows with common values in their common attribute(s).
When two or more tables share the same number of columns, and when their corresponding columns share the same or compatible domains, they are said to be _____.
The ____ relationship is the “relational model ideal.”
Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used
A(n) _____ is an orderly arrangement used to logically access rows in a table.
The practical significance of taking the logical view of a database is that it serves as a reminder of the simple file concept of data storage.
The idea of determination is unique to the database environment.
The entity relationship model (ERM) is dependent on the database type.
A composite identifier is a primary key composed of more than one attribute.
In implementation terms, an entity is existence-dependent if it has a mandatory primary key.
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
To simplify the conceptual design, most higher-order relationships are decomposed into appropriate equivalent _____ relationships whenever possible.
The existence of a(n) ___entity indicates that its minimum cardinality is zero.
In the entity relationship model, a table row corresponds to an entity instance.
a ____ relationship exists when three entities are associate.
A weak entity has a primary key that is partially or totally derived from the parent entity in the relationship.
If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a _____ relationship.
In Chen notation, there is no way to represent cardinality
In the original Chen notation, each attribute is represented by an oval with the attribute name connected to an entity rectangle with a line.
The first step in building an entity-relationship diagram (ERD) is ____.
creating a detailed narrative of the organization’s description of operations
An entity in the entity relationship model corresponds to a table in the relational environment.
The process of database design is a sequential process
The Crow’s Foot notation is less implementation-oriented than the Chen notation.
Software vendors have adopted the Chen representation because of its compact representation.
A derived attribute is indicated in the Chen notation by a _____ that connects the attribute and an entity.
dashed line
The conceptual model can handle ____ relationships and multivalued attributes.
In organizations that generate large number of transactions, _____ are often a top priority in database design.
high processing speeds
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.
One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.
Entity supertypes and subtypes are organized in a specialization hierarchy.
_____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.
Which of the following is a specialization hierarchy disjoint constraint scenario in case of partial completeness?
Subtype discriminator can be null
Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype.
Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
Overlapping subtypes are subtypes that contain ____ subsets of the supertype entity set.
In the context of total completeness, in a(n) _____, every supertype occurrence is a member of at least one subtype.
overlapping constraint
An entity cluster is a “virtual” entity type used to represent multiple entities and relationships in the ERD.
When selecting a foreign key placement for a 1:1 relationship, place the PK of the entity on the mandatory side in the entity on the optional side as a FK, and make the FK mandatory when _____.
one side is mandatory and the other side is optional
In the context of total completeness, in a(n) _____, every supertype occurrence is a member of only one subtype.
disjoint constraint
An entity cluster is formed by combining multiple interrelated entities into _____.
a single abstract entity object
The function of the primary key is to describe an entity
A _____ occurs when there is one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.
fan trap
The preferred placement for a foreign key when working with a 1:1 relationship is to _____.
place the foreign key in one of the entities
The property of _____ enables an entity subtype to inherit the attributes and relationships of the supertype.
To model time-variant data, one must create a new entity in an M:N relationship with the original entity.
The default comparison condition for the subtype discriminator attribute is the _____ comparison.
At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n) _____ relationship.
Surrogate primary keys are especially helpful when there is no ____ key.
Entity subtypes do not inherit the relationships in which the supertype entity participates.
Atomic attributes are attributes that can be further subdivided.
Normalization represents a micro view of the ___ within the ERD.
In a(n) ____ diagram, the arrows above the attributes indicate all desirable dependencies.
Of the following normal forms, ____ is mostly of theoretical interest.
In order to meet performance requirements, portions of the database design may need to be occasionally denormalized.
Data redundancy produces ____.
data integrity problems
A dependency based on only a part of a composite primary key is known as a partial dependency.
In a _____ situation, one key determines multiple values of two other attributes and those attributes are independent of each other.
multivalued dependency
Since a partial dependency can exist only if a table’s primary key is composed of several attributes, if a table in 1NF has a single-attribute primary key, then the table is automatically in 2NF.
Data stored at their highest level of granularity are said to be atomic data.
Most designers consider the BCNF as a special case of the ____.
For most business transactional databases, we should normalize relations into ____.
A table is in 4NF if it is in 3NF, and ____.
it has no multivalued dependencies
The most likely data type for a surrogate key is ____.
In a real-world environment, we must strike a balance between design integrity and _____.
A table where every determinant is a candidate key is said to be in _____.
Attributes should clearly define participation, connectivity, and document cardinality.
Data redundancy produces data anomalies.
The conflicts between design efficiency, information requirements, and performance are often resolved through _____.
compromises that include denormalization
When designing a database, you should ____.
make sure entities are in normal form before table structures are created
Improving ____ leads to more flexible queries.
We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy close
We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy