This page is for data modellers or application designers. It explains how to use a relationship diagram to understand how your system's data is connected.

Overview

Use a relationship diagram to represent the information that your application will use and how it is connected. If you want to show a process, use a workflow diagram.

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.

Sections on this page

Key concepts
Entity-Relationship Diagram	PhixFlow Relationship Diagram	Examples
A database table represents a thing or entity.	A stream represents a thing or entity. 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 relationships, expressed as an action (verb) that follows the left-right flow of the diagram. Relationships can be: one to one: from primary key to primary key one to many: from primary key to foreign key many to one: from foreign key to primary key many to many: from foreign key to foreign key 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

More About Relationships

The name for the relationship should reflect its direction. For example:

either company → employs → people
or people→ work for → company
but not company → work for→ people

PhixFlow imposes no restrictions on the names for relationships, but it must be unique in the repository.

Example

In a relationship diagram, a stream and its attributes are displayed as a box. You can expand or collapse the box using the icon in the top left. PhixFlow shows all the attributes when the stream is expanded, and only the primary and foreign keys when it is collapsed.

The following diagram shows some relationships between streams that represent a company, its employees and departments, the products it makes and the customers who buy them.

The company "contains" many departments. An employee "works in" a department, and a department can have many team members. In this company, the department "makes" several products, which "ship to" many customers.

Relationship diagrams are useful because you can design relational views that use data from multiple streams. For example, you might want a view that shows the employee details by department. This will display data from the Employee stream and the Department stream. The relationship diagram shows these are connected by the DepartmentID attribute.

How to Draw a Relationship Diagram

Create the Diagram

In the repository for your application, right-click on
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.
Click Add New.
In the pop-up, enter its name.
PhixFlow opens a properties tab on the right, and a new relationship diagram on the left. The relationship diagram has a toolbar at the top; see the Toolbar section below for details.

When you make any changes to the diagram, remember to Save.

Create a New Stream

Drag the
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icon from the toolbar into the diagram.
In the pop-up, enter its name, for example "Customer".
PhixFlow adds a box to represent the data stream, and opens the properties tab for it.
In the properties tab on the right, In the Attributes section, click Add New.
PhixFlow opens a properties tab where you can specify details for the attribute, such as its name, data type and length.
If this is the unique identifier, tick Primary Key. Remember to include ID or UID in the name.

Add an Existing Stream

In the repository, open the list of streams.
Drag a stream from the repository into the diagram.
If the stream has many attributes, click to collapse the stream so that it only shows the primary and foreign keys.

Connect Attributes

Click-drag from one attribute to another, PhixFlow shows the currently selected destination in bold. Release the click to connect to the selected destination.

PhixFlow can only connect primary and foreign keys. If you connect standard attributes, PhixFlow automatically sets them to be foreign keys.

PhixFlow automatically sets type of relationship according to the keys:

one to one: from primary key to primary key
one to many: from primary key to foreign key
many to one: from foreign key to primary key
many to many: from foreign key to foreign key

Other affected pages: repository, toolbars

Properties

For information about the properties toolbar, and about the sections Parent Details, Analysis Models, Description and Audit Summary, see Common Properties. We recommend you always add a Description that explains the purpose of the item you are creating.

For a full list of all the PhixFlow property tabs and windows, see Properties, Windows, Menus and Toolbars.

Basic Settings

Field	Description
Name	Enter the name for the entity-relationship diagram. When yo press Return or save a new properties tab, PhixFlow opens an empty diagram in the workspace on the left.

Drawing Entity-Relationship Diagrams

To create an ERD, in the application repository, right-click ERD and select Add New. PhixFlow opens the properties for diagram, where you can add the name and a description for it. When you press Return or save a new properties tab, PhixFlow opens an empty diagram in the workspace on the left.

Adding Entities

To open an existing ERD:

either, in the Repository, right-click the name and select Display.
or, in the properties toolbar, click the ERD icon (TODO add).

Entities are represented by streams and their attributes.

To add an existing stream, from the repository, drag an existing stream into the diagram. PhixFlow adds the stream and all of its attributes.

To add a new stream.

from the toolbar, drag the stream icon (TODO add) into the diagram.
Enter a name for the new stream and click . PhixFlow opens a new Stream properties tab.
To add attributes to an entity/stream:
either, in the stream properties → Attributes section toolbar, click Add New
or, right-click the stream and select Add New Stream Attribute.
In the new attribute properties, enter details for the Stream Attributes.

As streams can contain many attributes, you can collapse the view to show only primary and foreign keys. TODO ADD screenshot

Adding Relationships

To add a relationship, click on one attribute and drag the mouse pointer to an attribute in another stream. PhixFlow extends a red arrow line. Stop dragging, or click on an attribute name to connect the two. PhixFlow displays an attribute in bold when it has focus.

When you create a relationship, PhixFlow:

sets the origin attribute to be a Primary Key which must be unique.
sets the destination attribute to be a Foreign Key
creates a one-to-many relationship

The Primary Key and Foreign Key are properties of the Stream Attributes. (TODO ADD the new properties to attributes)

If both attributes are

primary keys, PhixFlow creates a one-to-one relationship.

foreigh keys, PhixFlow creates a many-to-many relationship.

If you connect two primary keys, PhixFlow creates a 1 to 1 relationship.

You cannot create a relationship between attributes if they are not a primary or foreign key. If you add a relationship between attributes, PhixFlow automatically sets them to be one of these.

ERDs and Relational Views

TODO - Add how ERDs and Relational vies interact.

TODO - Possibly bugs or possibly me...

I ended up with 3 streams that did not appear until the diagram is saved - can I reproduce this
relationship end points can be drawn a long way from the mouse.
I can untick keys and it keeps the relationship
When entities are below each other PhixFlow gets confused.

Toolbar

TODO Same as Model Window Toolbar Icons

	Organise selected objects in a grid.
	Align all selected objects left.
	Align all selected objects right.
	Align all selected objects to top.
	Align all selected objects to bottom.
	Distribute all selected objects horizontally. Changed ICON TODO
	Distribute all selected objects vertically. Changed ICON TODO
	Drag into the diagram to add a stream, or click to open the list of streams in the repository
	Save TODO
	Refresh TODO
	Help TODO