MIS 431 EXAM 2 STUDY GUIDE
ER Model - Answer -Entity Relationship Model
-represents conceptual view
Main Components:
1. Entities
-corresponds to entire table, not row
-represented by rectangle
2. Attributes
3. Relationships
Logical View of Data - Answer -Relational Database
Designer focuses on logical representation rather than physical
Advantages of usage of table - Answer -1. structural and data independence
2. related records stored in independent tables
3. logical simplicity
Allows for more effective design strategies
Elements of a Relational Database - Answer -1. Entity
2. Attribute
3. Relationship
Tables - Answer --Holds related entities or entity set
-Also called "relations"
-Comprised of rows and columns
Common Notations for ER Modeling - Answer -1. Chen's
2. Crow's Feet
-We use Crow's Feet for ER Model drawings in class
3. Modeling Language (UML)
Attributes - Answer --Characteristics of entities
-Domain is set of possible values
-Primary keys underlined
1. Simple- cannot be subdivided
2. Composite- can be further subdivided
3. Single-valued- only one possible value
-ex: can be single or composite
4. Multi-valued-can have multiple values
5. Derived-calculated from other attributes
-ex: age, GPA
, Types of Keys - Answer -Candidate Key (CK)-uniquely identifies a record/row
Primary Key (PK)-a chosen primary identification
Foreign Key (FK)-attribute in one table referencing another table
Keys - Answer -One or more attributes that determine other attributes
-key attribute
-composite key
Full functional dependence
-everything is dependent on primary key
Entity integrity
-uniqueness
-no "null" value in key
Integrity Rules - Answer -Entity Integrity
-ensures all entities are unique
-each entity has unique key
Referential Integrity
-foreign key must have null value or match primary key values
-makes it impossible to delete row whose primary key has mandatory matching foreign
key values in another table
ERD Symbols - Answer -A rectangle represents the entity type. Entities are named with
a noun.
A verb represents the relationship between entities
-the verb can be written above the line or if including relationship triangles, can be
written in the triangle
"1" side of relationship - Answer -no change in diagram (assumed to be one)
"Many" relationships - Answer -three pronged "Crow's foot" or an * (UML)
Entity Relationships - Answer -Indicates number of associated entities participating in
the relationship
Unary - Answer --Single entity
-Recursive
-Exists between occurrences of same entity set
Binary - Answer --Two entities associated
Ternary - Answer --Three or more entities associated
ER Model - Answer -Entity Relationship Model
-represents conceptual view
Main Components:
1. Entities
-corresponds to entire table, not row
-represented by rectangle
2. Attributes
3. Relationships
Logical View of Data - Answer -Relational Database
Designer focuses on logical representation rather than physical
Advantages of usage of table - Answer -1. structural and data independence
2. related records stored in independent tables
3. logical simplicity
Allows for more effective design strategies
Elements of a Relational Database - Answer -1. Entity
2. Attribute
3. Relationship
Tables - Answer --Holds related entities or entity set
-Also called "relations"
-Comprised of rows and columns
Common Notations for ER Modeling - Answer -1. Chen's
2. Crow's Feet
-We use Crow's Feet for ER Model drawings in class
3. Modeling Language (UML)
Attributes - Answer --Characteristics of entities
-Domain is set of possible values
-Primary keys underlined
1. Simple- cannot be subdivided
2. Composite- can be further subdivided
3. Single-valued- only one possible value
-ex: can be single or composite
4. Multi-valued-can have multiple values
5. Derived-calculated from other attributes
-ex: age, GPA
, Types of Keys - Answer -Candidate Key (CK)-uniquely identifies a record/row
Primary Key (PK)-a chosen primary identification
Foreign Key (FK)-attribute in one table referencing another table
Keys - Answer -One or more attributes that determine other attributes
-key attribute
-composite key
Full functional dependence
-everything is dependent on primary key
Entity integrity
-uniqueness
-no "null" value in key
Integrity Rules - Answer -Entity Integrity
-ensures all entities are unique
-each entity has unique key
Referential Integrity
-foreign key must have null value or match primary key values
-makes it impossible to delete row whose primary key has mandatory matching foreign
key values in another table
ERD Symbols - Answer -A rectangle represents the entity type. Entities are named with
a noun.
A verb represents the relationship between entities
-the verb can be written above the line or if including relationship triangles, can be
written in the triangle
"1" side of relationship - Answer -no change in diagram (assumed to be one)
"Many" relationships - Answer -three pronged "Crow's foot" or an * (UML)
Entity Relationships - Answer -Indicates number of associated entities participating in
the relationship
Unary - Answer --Single entity
-Recursive
-Exists between occurrences of same entity set
Binary - Answer --Two entities associated
Ternary - Answer --Three or more entities associated
