D426 WGU OA Final Exam Study Notes on Referential Integrity and Data Model
D426 WGU OA Final Exam Study Notes on Referential
Integrity and Data Model
1. What does modality refer to? How does it appear on a ER diagram?
a. Refers to the MINIUMUM number of times an instance in one entity can be
associated with instance of another entity(minima). Appears as a 0 or 1
on the relationship line, next to cardinality.
2. Define: Referential Integrity
a. Requires that ALL foreign key values must either be fully NULL or match
some primary key.
3. Four ways Referential Integrity can be violated:
a. Primary key is updated
b. Foreign key is updated
c. Row containing primary key is deleted
d. Row containing foreign key is inserted
4. Actions to Correct Referential Integrity Violation:
a. RESTRICT – rejects an insert, update or delete
b. SET NULL – sets invalid foreign keys to null
c. SET DEFAULT – sets invalid foreign keys to a default primary value
d. CASCADE – propagates primary key changes to foreign keys
5. What is an important aspect to referential integrity?
a. Reference to data in one relation is based on values in another relation.
6. What is a broad definition of data?
a. Raw facts captured or printed on digital media.
7. What are data?
a. Facts that are collection and stored in a database system.
8. What is a determining characteristic of unstructured data?
a. It does not follow a data model.
9. What is true about flat files?
a. They contain no internal hierarchical organization.
10. How were data retrieved before database management systems?
a. Sequentially from simple files
11. What is an attribute or group of attributes that uniquely identify a tuple in a
relation?
a. Primary Key
12. What is necessary for a primary key in one relation of a database to match with
its corresponding foreign key in another relation to the same database?
a. A domain of values
13. What uniquely identifies each entity in a collection of entities bus is not the
primary key?
a. Alternate Key
D426 WGU OA Final Exam Study Notes on Referential Integrity and Data Model
D426 WGU OA Final Exam Study Notes on Referential
Integrity and Data Model
1. What does modality refer to? How does it appear on a ER diagram?
a. Refers to the MINIUMUM number of times an instance in one entity can be
associated with instance of another entity(minima). Appears as a 0 or 1
on the relationship line, next to cardinality.
2. Define: Referential Integrity
a. Requires that ALL foreign key values must either be fully NULL or match
some primary key.
3. Four ways Referential Integrity can be violated:
a. Primary key is updated
b. Foreign key is updated
c. Row containing primary key is deleted
d. Row containing foreign key is inserted
4. Actions to Correct Referential Integrity Violation:
a. RESTRICT – rejects an insert, update or delete
b. SET NULL – sets invalid foreign keys to null
c. SET DEFAULT – sets invalid foreign keys to a default primary value
d. CASCADE – propagates primary key changes to foreign keys
5. What is an important aspect to referential integrity?
a. Reference to data in one relation is based on values in another relation.
6. What is a broad definition of data?
a. Raw facts captured or printed on digital media.
7. What are data?
a. Facts that are collection and stored in a database system.
8. What is a determining characteristic of unstructured data?
a. It does not follow a data model.
9. What is true about flat files?
a. They contain no internal hierarchical organization.
10. How were data retrieved before database management systems?
a. Sequentially from simple files
11. What is an attribute or group of attributes that uniquely identify a tuple in a
relation?
a. Primary Key
12. What is necessary for a primary key in one relation of a database to match with
its corresponding foreign key in another relation to the same database?
a. A domain of values
13. What uniquely identifies each entity in a collection of entities bus is not the
primary key?
a. Alternate Key
D426 WGU OA Final Exam Study Notes on Referential Integrity and Data Model
