Question

Please explain and describe

1. What is Arcs in ERD (Entity Relational Diagram)

2. What is Historical Data

3. What is the purpose of modeling Historical Data

4. What is Recursive Relationship in ERD

4. What is Recursive Relationship in ERD

Answer 1

1)

Arcs Representing Exclusive OR Relationships in the ERD

• Arcs are a way to represent mutually exclusive relationships in the ERD.
• An arc always belongs to one entity.
• Arcs can include more than two relationships.
• Not all relationships of an entity need to be include in an arc.
• An arc always should consistof relationships of the same optionality.
• All relationships in an arc must be mandatory or all must be optional.

2)

Historical data often includes the opening, high, low and closing values of an asset or index over a specific period of time. ... Historical data is often used to forecast future forex rate movements.

3)

The primary goal of using data model are: Ensures that all data objects required by the database are accurately represented. ... A data model helps design the database at the conceptual, physical and logical levels. Data Model structure helps to define the relational tables, primary and foreign keys and stored procedures.

4)

A relationship between two entities of similar entity type is called a recursive relationship. ... In other words, a relationship has always been between occurrences in two different entities. However, it is possible for the same entity to participate in the relationship. This is termed a recursive relationship.

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