This page is for....TODO

Overview

Use an entity relationship diagram are commonly used to draw out the relationships between data elements in a database. It helps you to visualise how the systems information is connected.

The components of a diagram

• Each "entity" is displayed as a box,  This is equivalent to a stream in PhixFlow
• Entities have attributes
• Entities usually have one attribute that is a unique Primary key.
  Foreign keys are linked to the primary key in another entity
• Relationships show how entities are connected
• Attributes
• between streams - entities ??
• between attributes. 

Relationships can be 1-to-1, 1-to-many or many-to-many. TODO - self-connected?

Creates

Contains

Has

To show the process flow of data, use a BPMN diagram

TODO purpose.

Other affected pages: repository, toolbars

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1. from the toolbar, drag the stream icon (TODO add) into the diagram.
   
2. Enter a name for the new stream and click

   Insert excerpt
   _dialog_finish _dialog_finish nopanel true

   . PhixFlow opens a new Stream properties tab.
   
3. To add attributes to an entity/stream:
   either, in the stream properties → Attributes section toolbar, click 

   Insert excerpt
   _add _add nopanel true

   
   or, right-click the stream and select Add New Stream Attribute.
4. In the new attribute properties, enter details for the Stream Attributes.

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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. Click 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:

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

If neither attribute is a key, or 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

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• I ended up with 3 streams that did not appear until the diagram is saved
• I tried to link 2 non-key attributes. The from point kept going to the primary key attribute. I had to drag the correct attribute from the stream attributes into the relationship.
• relationship end points can be drawn a long way from the mouse. 
• I can untick keys and it keeps the relationship

Toolbar

TODO Same as Model Window Toolbar Icons

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