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WorksheetsER Model Fundamentals
Total questions: 74
Worksheet time: 35mins
An entity is a
object of relation
present working model
thing in real world
model of relation
Which of the following is not a component of ER Model in DBMS?
entity
database
attribute
relationship
A relationship is
an item in an application
a meaningful dependency between entities
a collection of related entities
a related data
The expansion of ER Diagram is
Entity Relationship diagram
Entity Relative diagram
Entity Relation diagram
Entity Rationalized diagram
Entity is represented as
ellipse
double ellipse
rectangle
double rectangle
In one to many relationship, the entity that is on the one side of relationship is called
subtype
child
instance
parent
Property that describes the characteristics of entity is
entities
relationship
attributes
identifiers
Entities can be associated with one another in which of the following
attribute
identifiers
entities
relationship
By relation cardinality we mean
number of items in a relationship
number of relationships in which an entity can appear
number of items in an entity
number of entity sets which may be related to a given entity
If an entity appears in N relationship then it is
a 1:1 relationship
a 1:N relationship
a N:1 relationship
a N:M relationship
Rows of a relation is called
a relation row
an entity
a data structure
tuples
The columns of a relation
must be in specified order
may be in any order
with key field in first column
with largest width column last
Attributes are
properties of relationship
attributed to entities
properties of members of an entity set
In ER diagram relationships is represented by
circles
rectangles
ellipse
diamond shaped box
One entity may be
related to only one other entity
related to itself
related to only two other entities
related to many other entities
ERD stands for _________.
enhance relation diagram
entity responsive diagram
entity relationship diagram
enable relationship diagram
A data model is a ______________.
The mathematical model of formulas and logic used in a system
The abstract creating of an ideal system transformation
The expanded, thoroughly balanced and normalized use case for a system
A formal way of representing the data that are used and created by a business system
On an ERD _________________:
Processes are listed alphabetically with relationship connections drawn between processes
Data elements are listed alphabetically with a cross listing to the processes that manipulate them
Data elements are grouped in a hierarchical structure that is uniquely identified by number
Data elements are listed together and place inside boxes called entities
An entity ____________.
Has cardinality (1:1, 1:N, or M:N)
Shows if it can be null or no null
Is a person, place or thing
Is described with a verb phrase
Which would NOT likely be an attribute of an entity called “Student”?
Age
Student identification number
Class room number
Home phone
Gender
Lines on an ERD diagram indicate____________.
Hierarchies between processes
Relationships among the data
Plurality of data items
Uniqueness of data items
Primary keys
Data manipulation includes ________.
remove all tables in SQL.
Add, delete, modify, and retrieve using SQL
perform quality check on SQL
HOUSE/POSTCODE
For the following two ENTITIES, which is the appropriate relationship:
STUDENT/SUBJECT
One to One
One to Many
Many to Many
Each entity is described by __________.
entity
relationship
none of these
attribute
This key uniquely identifies each record in an entity.
Primary Key or Key Identifier
Foreign Key
Secondary Key
Composite Key
For ERD this shape describe for ?
Cardinality
Relationship
Attribute
Entity
Which of the following attributes can use to form composite attributes? [select all that apply]
Name
Address
Total
Age
The Primary key must be
Not Null
Unique
either a or b
both a and b
An entity that inherits its primary key from more than one other entity
Parent entity
⦁ Entity occurrence
Child entity
Associative entity
What is the primary purpose of the Enhanced Entity-Relationship (EER) model?
To replace the traditional E-R model
To extend the E-R model with additional modeling constructs
To simplify database design by removing relationships
To enforce strict one-to-one relationships in all cases
Which of the following best describes a supertype in the EER model?
A generic entity type with common attributes shared by its subtypes
A subgrouping of entities with distinct attributes
A relationship between two entities
A constraint that ensures uniqueness in a database
In the context of supertype/subtype relationships, attribute inheritance means:
In the context of supertype/subtype relationships, attribute inheritance means:
Subtypes inherit all attributes and relationships from the supertype
Only unique attributes are inherited by the subtypes
Each subtype must have completely different attributes from the supertype
What symbol represents a Total Specialization constraint in an EER diagram?
A single line
A dashed line
A double line
A diamond shape
If an instance of a supertype must be a member of at least one subtype, which rule applies?
Partial Specialization Rule
Total Specialization Rule
Disjoint Rule
Overlap Rule
A supertype/subtype hierarchy is used when:
All attributes are unique to individual entities
An entity has multiple categories with shared and unique attributes
Every entity is independent and has no common attributes
Every entity is independent and has no common attributes
The disjoint rule ensures that:
An instance of a supertype can belong to multiple subtypes
An instance of a supertype can only belong to one subtype
A supertype must always have multiple subtypes
The supertype can exist without any subtypes
A subtype discriminator is:
A unique identifier for each subtype
An attribute that determines which subtype an entity belongs to
A relationship between subtypes
A rule that forces specialization
Overlapping subtypes occur when:
An instance of a supertype can belong to multiple subtypes
An instance of a supertype must belong to only one subtype
A supertype has no attributes
Subtypes are unrelated to each other
What does a single line between a supertype and the circle in an EER diagram indicate?
Total specialization
Partial specialization
Disjoint constraints
Overlapping constraints
Which of the following is an example of generalization?
Creating an EMPLOYEE supertype from the entities MANAGER and ENGINEER
Dividing VEHICLE into subtypes CAR and TRUCK
Assigning unique attributes to each instance of an entity
Ensuring that an entity belongs to a subtype
Which of the following is not an advantage of using supertype/subtype relationships?
Reducing redundancy in data models
Allowing for more specific entity attributes
Simplifying complex database relationships
Eliminating the need for primary keys
Which of the following is an example of partial specialization?
Every instance of EMPLOYEE must be classified as either MANAGER or ENGINEER
Some instances of VEHICLE do not belong to any subtype
Every instance of VEHICLE must be either a CAR or a TRUCK
A supertype instance belongs to multiple subtypes
If a subtype has a composite subtype discriminator, it means:
The supertype has only one subtype
The discriminator has multiple attributes for different subtypes
Each subtype is independent from the supertype
Every subtype has the same attributes
Which constraint allows an entity to exist at the supertype level without being a subtype?
Total Specialization
Partial Specialization
Disjoint Rule
Attribute Inheritance
What does a double line from a supertype to a circle represent?
Total Specialization
Disjoint Rule
Overlapping Subtypes
Partial Specialization
What type of attribute is used to determine the subtype for an entity?
Foreign Key
Subtype Discriminator
Primary Key
Derived Attribute
Which scenario would require overlapping subtypes?
A database of books classified as Fiction or Non-Fiction
A student who can be both an athlete and a scholar
A vehicle that is either a car or a truck, but not both
A hospital where each patient must be an outpatient or inpatient
In an EER diagram, what does the letter "d" inside a circle indicate?
Disjoint rule
Overlap rule
Derived attribute
Double specialization
The "o" in an EER diagram signifies:
Overlapping subtypes
Disjoint subtypes
Optional attributes
Outdated entity types
What is the root in a supertype/subtype hierarchy?
The most specialized subtype
The entity with no attributes
The top-most supertype
The least important entity
What kind of relationship exists between a supertype and its subtypes?
Many-to-many
One-to-many
One-to-one
Many-to-one
In an employee database, which of the following would best represent an example of an EER model?
A single EMPLOYEE entity with all attributes
EMPLOYEE as a supertype with subtypes MANAGER and INTERN
Separate MANAGER and INTERN entities with duplicate attributes
A table without any hierarchical relationships
When should you use a supertype/subtype relationship in database modeling?
When all entities share the exact same attributes
When there are distinct categories of an entity with some shared attributes
When all attributes are unique to each entity
When multiple entities have no relationships
What type of specialization occurs when an instance of a supertype must belong to at least one subtype?
Partial specialization
Total specialization
Disjoint specialization
Composite specialization
If a supertype/subtype relationship has overlapping subtypes, how should its subtype discriminator be structured?
A single attribute with multiple values
A composite attribute with Boolean values for each subtype
A derived attribute from another entity
A primary key shared across all entities
In a supertype/subtype hierarchy, what ensures that all instances of a supertype fit into at least one subtype?
Disjoint rule
Overlapping rule
Total specialization
Partial specialization
In which scenario would a partial specialization rule be more appropriate?
Every EMPLOYEE must be classified as either a MANAGER or an ENGINEER
A VEHICLE entity where some vehicles are neither a CAR nor a TRUCK
A STUDENT entity where each student must be an UNDERGRADUATE or GRADUATE
A COMPANY entity where every company must be a startup or a corporation
If a database model includes an EMPLOYEE supertype with subtypes MANAGER and ENGINEER, and each employee can only be one subtype, what constraint applies?
Overlap rule
Disjoint rule
Total specialization
Partial specialization
A hospital has a PATIENT supertype with OUTPATIENT and INPATIENT subtypes. If every patient must be one or the other, but not both, which constraints apply?
Total specialization and overlap rule
Partial specialization and disjoint rule
Total specialization and disjoint rule
Partial specialization and overlap rule
If a supertype/subtype hierarchy has multiple levels of subtypes, what is this structure called?
Disjoint model
Generalization pattern
Supertype nesting
Supertype/subtype hierarchy
A company database tracks employees, alumni, and students under a PERSON supertype. If a person can be both an ALUMNUS and a STUDENT, which rule applies?
Disjoint rule
Overlapping rule
Partial specialization
Total specialization
Which of the following best describes the purpose of generalization in an EER model?
It reduces redundancy by creating a higher-level entity that encompasses multiple lower-level entities
It breaks down a broad entity into more specific subtypes
It ensures that every instance of a supertype is assigned to a subtype
It prevents an entity from inheriting attributes from multiple sources
Generalization is the process of defining a more specific entity type from an existing supertype.
true
false
The Disjoint Rule ensures an instance can only belong to one subtype.
true
false
A supertype/subtype hierarchy can only have two levels.
true
false
The Partial Specialization Rule means that not all instances of a supertype must belong to a subtype.
true
false
Overlapping subtypes require the use of composite subtype discriminators.
true
false
In an EER diagram, a double line represents a partial specialization constraint.
true
false
A supertype may have multiple subtypes, but each subtype can only belong to one supertype.
true
false
The Overlap Rule allows an instance of a supertype to be a member of multiple subtypes.
true
false
