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What is an entity relationship?

What is an entity relationship?. A Entity Relationship Diagram is a graphical representation of entities and their relationships to each other, typically used in computing in regard to the organization of data within databases or information systems. What are the symbols used in the E.r.d.

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What is an entity relationship?

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  1. What is an entity relationship? A Entity Relationship Diagram is a graphical representation of entities and their relationships to each other, typically used in computing in regard to the organization of data within databases or information systems.

  2. What are the symbols used in the E.r.d

  3. Entity An entity is something that has a distinct, separate existence, though it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. Symbol

  4. Attributes An attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such. Symbol

  5. Relationship A relationship captures how two or more entities are related to one another. Relationships can known as be verbs, linking two or more nouns. Symbol

  6. What is one-to-one relationship one-to-one: one instance of an entity (D) is associated with one other instance of another entity (F). For example, in a database of employees, each employee name (D) is associated with only one social security number (F).

  7. What is a one-to-many relationship one-to-many: one instance of an entity (D) is associated with zero, one or many instances of another entity (E), but for one instance of entity E there is only one instance of entity D. For example, for a company with all employees working in one building, the building name (D) is associated with many different employees (E), but those employees all share the same singular association with entity D.

  8. What is a many-to-many relationship many-to-many: one instance of an entity (D) is associated with one, zero or many instances of another entity (E), and one instance of entity E is associated with one, zero or many instances of entity D. For example, for a company in which all of its employees work on multiple projects, each instance of an employee (D) is associated with many instances of a project (E), and at the same time, each instance of a project (E) has multiple employees (D) associated with it.

  9. Vanessa Edwards presentation The End

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