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. 

One to One Relationships

In a PhixFlow relationship diagram, it is not possible to create a one-to-one relationship. 

Many-to-Many Relationships

You can show a many-to-many relationship by using an intermediate stream, called a resolution entity. This has foreign keys from the two streams you want to connect, with a one-to-many relationship into the foreign keys. For example

• A customer buys many products
• And a product can be bought by many customers

In this case the resolution entity could be the customer purchase record, which has both the CustomerID and ProductID as foreign keys

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.

Relationship Diagrams and Relational Views

TODO - Add how ERDs and Relational vies interact.

Drawing Relationship Diagrams

Create a Relationship Diagram

1. In the repository for your application, right-click on 

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   .
2. Click 

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   .
3. In the pop-up, enter its name.
4. 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.

Open a Relationship Diagram

To open an existing relationship diagram:

• either, in the repository, right-click on its name and select Display.
• or, in the properties toolbar, click the .

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  _relationship_diagram _relationship_diagram nopanel true

   icon.

Create a New Stream

1. Drag the 

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    icon from the toolbar into the diagram.
2. In the pop-up, enter its name, for example "Customer" and click

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   . PhixFlow opens a new Stream properties tab.
3. PhixFlow adds a box to represent the data stream, and opens the properties tab for it.
4. To add attributes to the stream
   • either, in the properties tab on the right, In the Attributes section, click 

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     .
   • or right-click the stream and select Add New Stream Attribute.
5. PhixFlow opens a Stream Attributes properties tab where you can specify details for the attribute, such as its name, data type and length. 
6. If this is the unique identifier, tick Primary Key. Remember to include ID or UID in the name.

Add an Existing Stream

1. In the repository, open the list of streams.
2. Drag a stream from the repository into the diagram. PhixFlow adds the stream with a list of all of its attributes.
3. If the stream has many attributes, click  to collapse the stream so that it only shows the primary and foreign keys.

Connect Attributes

To connect attributes in different streams, 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 the 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

Basic Settings

Toolbar 

Anchor
toolbar 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