W7 L2 - Data Modelling

Question 1

What is the goal of Data design and modelling

Answer 1

understand the data, what data is needed and not needed

Question 2

What is an Entity?

Answer 2

An entity is any object in the system that we want to model and store information about. Entities are usually recognizable concepts, either concrete or abstract, such as person, places, things, or events which have relevance to the database. Some specific examples of entities are Employee, Student, Lecturer.

Question 3

What is an Attribute?

Answer 3

An ERD attribute can be denoted as a primary key, which identifies a unique attribute, or a foreign key, which can be assigned to multiple attributes. The relationships between and among those entities.

Question 4

What is a Relationship?

Answer 4

An Entity Relationship (ER) Diagram is a type of flowchart that illustrates how “entities” such as people, objects or concepts relate to each other within a system

Question 5

What is a cardinality?

Answer 5

Cardinality refers to the uniqueness of data values contained in a column. High cardinality means that the column contains a large percentage of totally unique values. Low cardinality means that the column contains a lot of “repeats” in its data range.

Question 6

Draw the cardinalities

Answer 6

Mandatory one

Optional one (zero or one)

Mandatory many (one, or more)

Optional many (zero, one, or more)