The Relational Model
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1
What is a table (relation) in the relational model?
A matrix consisting of row/column intersections.
2
How are tables related to each other in a relational database?
Through shared common entity characteristics.
3
What does a relational table store?
A collection of related entities.
4
What does the relational model allow users to do regarding data storage?
View data logically, independent of physical storage.
5
What is a key in the relational model?
One or more attributes that determine other attributes.
6
What is determination?
Knowing the value of attribute A allows you to determine the value of attribute B.
7
What is a Candidate Key (CK)?
A column or combination of columns that can uniquely identify rows and could serve as a Primary Key.
8
What is the Primary Key (PK)?
An attribute or combination of attributes that uniquely identifies any row in a table.
9
What is a requirement for a Primary Key (PK)?
It must be unique, non-repeating, and contain no NULL values.
10
What is a Foreign Key (FK)?
An attribute whose values match the Primary Key values of a related table.
11
What is a Composite Key?
A primary key made up of more than one attribute.
12
What do nulls represent in a table?
No data, a missing value, or a “not applicable” condition.
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Are nulls allowed in a Primary Key?
No, nulls are not permitted in a Primary Key.
14
What is Referential Integrity?
A rule stating that every FK value must refer to an existing valid row in another relation.
15
What is Entity Integrity?
A rule requiring that the Primary Key of a table must not contain null values.
16
What is controlled redundancy?
Using shared attributes (FKs) to link tables; repeated values are acceptable when needed for relationships.
17
What is a 1:M relationship?
A one-to-many relationship—the ideal and most common in relational design.
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What is a 1:1 relationship?
A one-to-one relationship, rare and sometimes a sign of improper entity definition.
19
What is an M:N relationship?
A many-to-many relationship that cannot be directly implemented in the relational model.
20
How is an M:N relationship resolved?
By creating a composite (bridge) entity that converts it into two 1:M relationships.
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