Student Information Sytem ER Diagram

student information system er diagram

Student Information System ER Diagram (Entity Relationship Diagram) illustrate the logical structure of databases. An Entity Relationship Diagram is a piece of data-an object or concept about which data is stored.

Student Information Sytem ER Diagram

There are three types of relationships between entities:

• one-to-one (1 to 1): one instance of an entity (A) is associated with one other instance of another entity (B). For example, in a database of employees, each employee name (A) is associated with only one social security number (B).

• one-to-many (1 to N): one instance of an entity (A) is associated with zero, one or many instances of another entity (B), but for one instance of entity B there is only one instance of entity A. For example, for a company with all employees working in one building, the building name (A) is associated with many different employees (B), but those employees all share the same singular association with entity A.

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

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