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PhixFlow's relationship diagrams are simplified entity-relationship diagrams (ERD). An ERD is commonly used to show the relationships between database tables. If you are not familiar with ERDs for databases, the concepts are explained in this article: ER Diagram Tutorial in DBMS.

Key concepts

Entity-Relationship Diagram

PhixFlow Relationship Diagram

Examples

A database table represents a thing or entity.

A stream represents a thing or entity.

Tip
Choose a stream name that reflects the entity it represents.

Entities:

Company
Employee
Department
Product

The column headers of a database table are the data attributes.

The stream attributes are the data attributes.

Employee attributes:

EmployeeID
Name
Address
Phone
Department

A stream must include one unique attribute. This is usually an identifier, so has ID or UID in the name. The unique attribute is the primary key.

Primary Keys

Employee stream: EmployeeID
Department stream: DepartmentID

When the data from one stream's primary key also appears in a different stream, it is a foreign key.

Employee attributes:

EmployeeID (primary key)
Name
Address
Phone
Department = DepartmentID - foreign key

Department attributes

DepartmentID - primary key
Department Name
Purpose
Team members = list of EmployeeID's = foreign key

Tables or attributes can have various relationships to each other

Attributes can have the following relationships

primary key → one to one → primary key
primary key → one to many → foreign key
foreign key → many to many → foreign key

Tip
Choose a relationship name that reflects the relationship

Relationships

one company → employs → many employee
one employee → works in → one department
one department → makes → many products

Relationships are usually expressed as an action (verb) that follows the left-right flow of the diagram. For example:

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