Understanding Entity Relationships

What are the different types of entities in a database?

• Tables, Rows, Columns, Relationships, Views

• Stored Procedures

• Triggers

• Indexes

Define the term 'attribute' in the context of databases.

• An attribute is a unique identifier for a database record.

• An attribute is a property or characteristic of an entity in a database, represented as a column in a table.

• An attribute refers to the entire database structure.

• An attribute is a type of database that stores multiple tables.

What is the difference between a simple attribute and a composite attribute?

• A simple attribute is always numeric, while a composite attribute is always textual.

• A simple attribute can hold multiple values, while a composite attribute holds a single value.

• A simple attribute can be broken down into sub-attributes, while a composite attribute cannot.

• A simple attribute holds a single value, while a composite attribute can be broken down into multiple sub-attributes.

Explain what a derived attribute is with an example.

• 'height' calculated from 'weight'

• 'salary' based on 'job title'

• An example of a derived attribute is 'age', which is calculated from 'date of birth'.

• 'name' derived from 'email'

What does the term 'degree of relationship' refer to in an ER diagram?

• The term 'degree of relationship' refers to the number of entities involved in a relationship in an ER diagram.

• The term 'degree of relationship' indicates the type of relationship between entities in an ER diagram.

• The term 'degree of relationship' refers to the strength of a relationship in an ER diagram.

• The term 'degree of relationship' describes the attributes of an entity in an ER diagram.

How many entities are involved in a unary relationship?

• Three entities

• One entity

• No entities

• Two entities

What is a binary relationship? Give an example.

• Students take Exams

• Teachers assign Grades

• Courses are taught by Students

• An example of a binary relationship is 'Students enroll in Courses'.

Define cardinality in the context of relationship sets.

• Cardinality refers to the total number of attributes in a relationship set.

• Cardinality indicates the strength of a relationship between entities.

• Cardinality is the process of defining the types of relationships in a database.

• Cardinality defines the number of instances in a relationship set, indicating the nature of the relationship (one-to-one, one-to-many, many-to-one, many-to-many).

What are the different types of cardinality?

• Two-to-Many

• One-to-One, One-to-Many, Many-to-One, Many-to-Many

• Many-to-Some

• One-to-Two

Explain the concept of one-to-one cardinality with an example.

• One-to-one cardinality refers to the relationship between a teacher and all their students.

• One-to-one cardinality is illustrated by the connection between books and their authors.

• One-to-one cardinality is exemplified by the relationship between students and their unique student IDs.

• One-to-one cardinality means that each student can have multiple student IDs.