This page is for application designers who want define the data that will back the application. It explains how to draw an ERD and setup its properties.

Overview

Use an ERD to define the structure of the data that backs your application. For an introduction to ERD concepts and why ERDs are important, see Understanding ERDs and Views.

The process for creating an ERD is slightly different depending on whether or not you have already created streams in PhixFlow. The following stream summarises the different ways you can add streams to an ERD, depending on your starting point. (See the sections below for details of how to add streams and relationships.)

Sections on this page

Starting Point

Process

Primary Key

See

I have no data

Define the streams, attributes and their relationships in the ERD.

Later you will need to add records to the streams:

either manually, for example create a screen in which application users can enter data.
or via an analysis model.

PhixFlow automatically creates each stream with:

a primary key called UID
a Name attribute
the Name attribute set as the display name; see Display Name.

Adding Content to an ERD

Creating a Screen from a Stream
Load Data

I have data but it's not in PhixFlow

Use an analysis model to connect to your data. PhixFlow can read the data structures to create stream. When you run analysis on the model, PhixFlow loads the data records.

In each stream:

either set one attribute as the primary key and ensure all values will be unique
or add an attribute called UID with
- Data Type = Integer
- Precision = 10
Set one attribute to be the Display Name.

Load Data

I have streams in PhixFlow already

In the ERD toolbar, click List Tables to display a list of all the streams. Drag streams into the ERD and then add the relationships.

Adding Content to an ERD

PhixFlow cannot ensure unique values for a primary key where:

the name is UID but its data type is not integer
the name is not UID

If your data already has a unique attribute, you can use that as the primary key. For example, the Teacher table could have a National Insurance attribute, which would be unique to a teacher. In this case, you must set up your own processes to make sure that the records in a table all have unique values in the primary key.

How to Define an ERD

Open an Existing ERD

In the repository, find ERD.

Either right-click on an ERD name and select Display.
Or double-click the ERD name to open the properties. In the properties toolbar, click the Display icon.

Create a New ERD

In the repository, find ERD. Right-click to display the context menu, and select Add New
Enter a name for your ERD, and a description then click Apply and Close.

When you are creating streams, choose a name that reflects the entity your stream represents.
PhixFlow opens a new ERD canvas on the left with a toolbar at the top. Hover your mouse pointer over toolbar icons to display a tooltip.

Add an Existing Stream

In the toolbar, click List Tables.
PhixFlow filters the repository to show the list of streams available in this application.
Drag a stream from the repository onto the ERD canvas.

Create a New Stream

Drag Create New Table from the toolbar into the diagram.
In the pop-up, enter a name, for example "Customer", and click .
PhixFlow opens the properties tab for the new stream on the right and adds the stream to the canvas.
The header displays the name entered in step 2. PhixFlow automatically adds 2 attributes:

- UID - PhixFlow requires a unique identifier and primary key for each stream.
- Name - PhixFlow sets the Name attribute to be the display name. In data grids and forms etc. PhixFlow uses this attribute to provide a user-friendly name, rather than a numeric identifier. Optionally, change the attribute name.
To add attributes to the stream:
1. In the stream, click Create New. PhixFlow opens the attribute properties on the right, with the default settings of:
  - Type = String
  - Length = 50 characters.
2. In the properties, enter the Name and select appropriate type properties, such as Date or Integer; see Attributes. The following data types have additional properties:
  - For String add Length
  - For Integer add Precision
  - For Decimal add Significant Figures and Decimal Places
3. Click Apply and Close to save the attribute properties.
PhixFlow adds the attribute to the stream in the ERD.

Create Relationships

In an ERD you can create a one-to-many relationship between a primary key in one stream with an attribute in another stream. For relationship concepts, see Understanding ERDs and Views.

To create a relationship, click-drag from one attribute to another.

More detail

Click on the source attribute.
Drag to the destination attribute. PhixFlow highlights the attribute when your mouse pointer is over it.
When the destination attribute is highlighted, release the click.

See the stream below for the relationships that can be created between attributes.

Drag		Relationship line
From stream1	To stream2	Relationship line
primary key	attribute	stream1.primarykey → stream2.attribute 1:many
attribute	primary key	stream2.primarykey → stream1.attribute 1:many
attribute	attribute	if stream1 has no primary key: PhixFlow makes the stream1.attribute the primary key if stream 1 has a primary key: the relationship is from stream1.primarykey instead of from stream1.attribute.

PhixFlow cannot create a relationship between your selected attributes if your selected foreign key attribute:

is already a foreign key to a different primary key.
has a different Data Type and type properties to the primary key.

In these cases, PhixFlow reports an error: Related attributes must have the same type and length. This type/length is different.

If this happens, you can:

create a new attribute to be the foreign key
change the foreign key attributes to match the primary key, provided there is no data in the stream
create the relationship with a different attribute.

To change the data type properties, In the ERD, click on an attribute to open its properties.

If you have created several ERDs to define the data structure that your application requires, then each ERD is a view onto a part of the full data structure.

Show Relationships From Other ERDs

If you have created several ERDs to define the data structure that your application requires, then each ERD is a view onto a part of the full data structure.

If a stream appears on more than one ERD it may have relationships with streams that are not visible in your current ERD. To see other related streams, right-click a stream to show the context menu and select:

Show many to one relations Todo Todo-Fiona - check icons Show many-to-one relations
Show one to many relations Todo-Fiona - check icons Show one-to-many relations

PhixFlow adds the related streams to your ERD.

To keep the related streams in your ERD, in the toolbar, click Apply.

To remove the related streams from your ERD, in the toolbar, click Refresh.

Saving ERDs

Changes to streams, attributes and relationships are automatically saved. However, to keep any changes you make to the layout of a diagram, such as moving streams or adding angle points to relationships, remember to click Apply in the toolbar. PhixFlow notifies you if there are unsaved changes when you attempt to close an ERD.

Accessing Properties

You can set properties for all the items in an ERD. To access properties:

for the ERD: in the canvas toolbar click Properties
for a stream: in the ERD, click on the stream header or right-click to open the pop-up menu and select Configure
for an attribute: in the stream, click on an attribute
for a relationship: in the ERD, click on the relationship line. For relationships you can only add or change the description.

PhixFlow opens the properties panel on the right.

Rearranging ERDs

To move streams around in the ERD, click on the header and drag the stream. There are also Align options in the toolbar that you can use to line up or distribute selected streams.

If you want to highlight the relationships that affect a stream, click the stream to select it. The following screenshot shows the Teacher stream is selected.

Blue lines indicate relationships to a foreign key in the selected stream
Green lines indicate relationships from the primary key in the selected stream.

If a stream has a lot of attributes that you do not need to see, collapse the list to show only the stream's primary and foreign keys.

Either right-click on a stream and select Hide attributes or Show attributes
Or double-click on the stream header.

To select multiple streams, draw a square around them.

Hover your mouse pointer over
an angle to see the blue angle point.

By default, relationships are straight lines, but you can change them to have angles.

Click on a relationship line to add an angle point, which appears as a blue dot; see the screenshot on the left.
Move the mouse pointer over the blue dot. It changes to a four-way arrow to indicate you can drag.
Drag the point to the position you require.

To remove an unwanted angle, right-click the blue dot and select Remove Point; see the screenshot on the right.

Right-click the blue angle point to see the Remove option

Properties

Parent Details

If this item is within or belongs to another, its parent name is shown here. See the Parent Details section on the Common Properties page for more details.

Basic Settings

Field	Description
Name	The name for the ERD.

Description

We recommend that you always enter a description to explain the purpose of this item.

Audit Tab

Audit Summary

See the Common Properties page, Audit Summary section.

Toolbars and Popup Menus

ERD Toolbar

The toolbar is at the top of the canvas. Hover your mouse pointer over the toolbar to see a tooltip.

Option	Description
Create options
Table	Drag this icon onto the canvas to create a stream.
List options
Table	Click to open the repository filtered to list the streams available in your application.
Canvas options
Help	Open the help topic with details about working with ERDs.
Arrange Selected Items	Options to arrange the selected streams in the ERD: Align to Grid Align Objects to Left Align Objects to Right Align Objects to Top Align to base Error rendering macro 'excerpt-include' : No link could be created for '_distribute_horizontal'. Error rendering macro 'excerpt-include' : No link could be created for '_distribute_vertical'.
Properties	Open the properties tab for the ERD.
Zoom Out	Zoom out to see more of the diagram, with smaller text.
Zoom In	Zoom in to see a smaller area of the diagram, with larger text.
Apply	PhixFlow automatically saves changes to streams and relationships. Use this icon to save diagram layout changes to the ERD.
Refresh	Update the ERD to the last saved diagram layout. This clears any unsaved layout changes. Your ERD should automatically show an changes elsewhere in PhixFlow. For example, if someone adds a new attribute to a stream in your ERD, the attribute will appear on the list. If changes are not appearing, click this icon.
Ungroup todo-Fiona - does not seem to be available	Select a grouped set of items and then click to ungroup them. Select several items then click to group them together.

Stream Pop-up Menu

To access more options in a pop-up menu, in the stream header, click More Options

Option	Description
Configure todo-Fiona - check Can this be Properties	Open the properties for this stream.
Remove	Remove the selected item(s) from the diagram.
Show many to one relations todo-Fiona - should be Show one-to-many relations	Streams may have relationships to other streams not represented on the current ERD. Use these options to add all related streams to your ERD so that you can see the full relationship set; see Show Relationships From Other ERDs , above.
Show one to many relations todo-Fiona - should be Show many-to-one relations
Show or Hide Attributes	Toggle the stream between expanded to show all attributes or collapsed to show only the stream name, primary key and any foreign keys. This is useful if your stream contains many attributes.
Delete	Delete the selected item(s) from the ERD and from everywhere it is used.

Attribute Pop-up Menu

Option	Description
Make/Unset Primary Key	Set the current attribute to be a primary key. Remember to unset any other primary key in the stream.
Make/Unset Foreign Key	Set the current attribute to be a foreign key.
Attributes	Create a new attribute for the stream. PhixFlow opens the properties where you can add a name and set the data type.
Delete attribute	Delete the attribute from the stream. PhixFlow prompts you to confirm.

Defining Data Structures using ERDs