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.

ERD is still asking for a relationship name.

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.

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

Sections on this page

Starting Point

Process

Primary Key

See

I have no data

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

Later you will need to add records to the tables:

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

PhixFlow automatically creates each table with:

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

Defining Data Structures using ERDs

Creating a Screen from a Table
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 tables. When you run analysis on the model, PhixFlow loads the data records.

In each table:

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 tables in PhixFlow already

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

Defining Data Structures using ERDs

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 tables, choose a name that reflects the entity your table 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 Table

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

Create a New Table

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 table on the right and adds the table 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 table.
- 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 table:
1. In the table, 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 table in the ERD.

Create Relationships

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

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 table below for the relationships that can be created between attributes.

Drag		Relationship line
From table1	To table2	Relationship line
primary key	attribute	table1.primarykey → table2.attribute 1:many
attribute	primary key	table2.primarykey → table1.attribute 1:many
attribute	attribute	if table1 has no primary key: PhixFlow makes the table1.attribute the primary key if table 1 has a primary key: the relationship is from table1.primarykey instead of from table1.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.

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 table
create the relationship with a different attribute.

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

Show Relationships From Other ERDs

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

Show many-to-one relations
Show one-to-many relations

Saving ERDs

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

Rearranging ERDs

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

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

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

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

either right-click on a table and select Hide attributes or Show attributes
or double-click on the table header.

To select multiple tables, draw a square around them.

By default, relationships are straight lines, but you can change them to have angles (shown in the screenshot on the left).

Click on a relationship line to add an angle point, which appears as a blue dot.
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 (shown in the screenshot on the right).

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.

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
Create	Drag this icon onto the canvas to create a table.
Screen	Creates a new screen for the selected table.
List
Tables	Click to see a list available tables.
Screens	Click to see a list available screens.
Canvas
Save	Save changes to the diagram. If there is no save icon, PhixFlow is saving changes automatically.
Refresh	Redraw the ERD to display recent changes to the diagram.
Properties	Open the properties for the current diagram.
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.
Ungroup	Select a grouped set of items and then click to ungroup them. Select several items then click to group them together.
Group	Select several items then click to group them together.
Back	For screen layout, move a component back.
Forward	For screen layout, bring a component forward.
Align options	Click/hover to show all the options for aligning items on the canvas.
Align Grid	Organise selected items into a grid pattern.
Align left	Align selected items to the left.
Align right	Align selected items to the right.
Align top	Align selected objects to the top.
Align bottom	Align selected objects to the bottom.
Distribute horizontally	For 3 or more items, distributes the selected items evenly between the left and right items.
Distribute vertically	For 3 or more items, distributes the selected items evenly between the top and bottom items.

Table Pop-up Menu

You can access more options in a pop-up menu:

in the table header, click More Options
right-click anywhere in the table.

Option	Rename to	Description
Configure Table	Table properties	Open the properties for this table.
Remove this item from the Diagram	Remove from ERD	Remove the selected item(s) from the diagram.
Hide Attributes	Hide attributes	Collapse the table so that it only shows the table name, primary key and any foreign keys. Other attributes are hidden.
Show Attributes	Show attributes	Expand the table to show all the attributes
Parmanently Delete	Delete everywhere	DDelete the selected item(s) from the ERD and from everywhere it is used.

Defining Data Structures using ERDs

Overview

How to Define an ERD

Open an Existing ERD

Create a New ERD

Add an Existing Table

Create a New Table

Create Relationships

Show Relationships From Other ERDs

Saving ERDs

Rearranging ERDs

Properties

Parent Details

Basic Settings

Description

Audit Tab

Audit Summary

ERD Toolbar

Create

List

Canvas

Table Pop-up Menu