18 Questions
What is a relation in the context of a Relational DBMS?
A two-dimensional table
In a relation, what do columns typically contain?
Data about attributes of the entities
What is a characteristic of entries in a column in a relation?
They are of the same kind
How many primary keys can a relation have according to the text?
One
What is the purpose of candidate keys in a relation?
To identify rows uniquely
Which of the following is NOT a characteristic of relations in a Relational DBMS?
There can be multivalued attributes
What is the solid line connecting an I D-dependent entity and its parent called?
Identifying relationship
Which type of entity is considered weak?
ID-Dependent entity
What is a weak entity in data modeling?
An entity whose existence depends on another entity
Which type of relationship is used to represent ID-Dependent entities?
Identifying relationship
What is the dashed line connecting strong entities or non-ID-dependent weak entities to their parent called?
Nonidentifying relationship
How are weak entities that are not ID-Dependent represented in data modeling tools?
With nonidentifying relationships
What is the purpose of an intersection table in a N:M relationship between strong entities?
To hold the relationships between two strong entities
In an association table, what additional feature does it have compared to an intersection table?
It includes attributes specific to the associations of the other two entities
What occurs in a cascading update between a parent and child in a database?
Child's primary key changes when parent's primary key changes
When is cascading delete generally applied for strong entities?
Always
What type of entities do not require cascading updates when changes are made?
Surrogate key-dependent entities
What does an intersection table hold in a N:M relationship?
Only the primary keys of the two entities
Learn about the transformation of a many-to-many relationship between strong entities using intersection and association tables. Understand the differences between them and how cascading updates and deletes work in such relationships.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
