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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.

Think about the structure here Make it easier to track through. We need to be mindful "if you've got data"

Bring in an excel file creates the data structure (creates the table) but that's no the same as running analysis and then loading the data (analysis pulls in the records)


The things you need to consider when defining an ERD depend on whether or not you have already loaded data into PhixFlow. It feels like we are jumping into the middle here a little. How to define an ERD for me feels more of a natural starting point happy to discuss.

  • Make sure people are clear that PhixFlow can make this is you already have something
  • You have got data
  • You've got data NOT in PhixFlow
    • bring it in via a model
    • OR if its in Excel you can bring it in and create the model in 1 step
  • You've got data in PhixFlow (via model)
    If you have already loaded data (link to analysis model) (both table and records), the tables are listed in the repository. I feel there is a clash here against the statement earlier "it has not been loaded yet" as we can load a file without pulling data into PhixFlow. This then sets up the table structure for us.
    1. Drag tables from the repository Data → Tables into the ERD canvas. Again we want to avoid the respository we have the show tables option on an ERD.
    2. Set the primary key:
      • Either create an attribute called UID that PhixFlow will populate with unique values for each record
      • Or select an attribute to be the primary key. You will need to ensure this contains unique values.
      • If you add an excel file we have discussed presenting users with the option to select a Primary Key and Display Name. There is a flow that covers this see 4.10.
    3.  Add relationships
      • Should we state that users need to drag and drop to create a relationship? Dragging and dropping onto an attribute creates the relationship. Dragging and dropping onto the header bar creates the corresponding attribute and relationship.
      • Primary key and foreign key attributes must have the same data Type.
  • If you do not have any data for your application:
    1. Create tables, attributes and relationships in the ERD.
      • New tables have an attribute called UID, which is the primary key. We also create a Name attribute that is set to Display Name
      • Make sure the data Type is correct for the data that will populate each attribute. we haven't introduced the concept of creating attributes at this point, should we discuss setting a value?
      • PhixFlow adds table items to the repository. Attributes are listed within the Table properties. Should we say this as we are trying to avoid people browsing the repository, and we have the view table button on the in context menu.
      • Relationships are not listed in the repository. To see relationship properties, in the ERD, click the relationship arrow. should we go with the positive view point and say relationship details are only available on the ERD?
    2. Add records to your tables:
      • either manually e.g. create a screen to allow users to enter data.
      • or from an external source, e.g. Excel file, database etc. we need to consider what to tell people, as excel can be added directly but databases et al need an analysis model to back them. lets discuss our message. Also we say add records from an external source and have no information about that?
  • If you have already loaded data, the tables are listed in the repository. I feel there is a clash here against the statement earlier "it has not been loaded yet" as we can load a file without pulling data into PhixFlow. This then sets up the table structure for us.
    1. Drag tables from the repository Data → Tables into the ERD canvas. Again we want to avoid the respository we have the show tables option on an ERD.
    2. Set the primary key:
      • Either create an attribute called UID that PhixFlow will populate with unique values for each record
      • Or select an attribute to be the primary key. You will need to ensure this contains unique values.
      • If you add an excel file we have discussed presenting users with the option to select a Primary Key and Display Name. There is a flow that covers this see 4.10.
    3.  Add relationships
      • Should we state that users need to drag and drop to create a relationship? Dragging and dropping onto an attribute creates the relationship. Dragging and dropping onto the header bar creates the corresponding attribute and relationship.
      • Primary key and foreign key attributes must have the same data Type.



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How to Define an ERD

Open an Existing ERD

  1. From the home menu, select Data and click on an ERD in the list.
  2. In the repository, open your application and find Data → 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
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       icon.

Create a New ERD

  1. From the home menu, select Data.
  2. PhixFlow displays the list of ERDs. Select Create New from the left hand side.

  3. In the pop-up, enter a name for your ERD, and a description then click 

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    Tip

    When you are creating tables, choose a name that reflects the entity your table represents. Move to creationShould this be on the defining data structures page as we do not cover creation here?


  4. 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

  1. In the toolbar, click Table ListThe icon is called tables and the icon here is wrong as it includes the category name. Review the context menus for full details and please take the icons from the Icon repository directory on sharepoint. 
  2. PhixFlow filters the repository to show the list of tables available in this application.
  3. Drag a table from the repository onto the ERD canvas. 

Create a New Table

  1. Drag Table Create from the toolbar into the diagram.
  2. In the pop-up, enter a name, for example "Customer" and click
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  3. PhixFlow adds the table to the canvas and opens its properties tab on the right. Rhe header displays the name entered in step 2. PhixFlow automatically adds 2 attributes:
    • UID - the unique identifier and primary key.
    • Name -  (which also gets auto added and set as the display name - concept to explain)
  2. To add attributes to the table:
    1. In the table, click 
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      . PhixFlow opens the attribute properties on the right.
    2. In the properties, enter the Name, Type and Length for the data; see Attributes.
      PhixFlow creates attributes with a Type or String and Length of 50 characters. Remember to select appropriate type properties for an attributes data, such as Date or Integer.
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       the attribute properties.
  3. PhixFlow adds the attribute to the table in the ERD.
Tip

Changes to tables, attributes and relationships are automatically saved to the ERD. However, you must click 

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 to keep any changes you make to the layout, such as moving tables or adding corners to relationships.

What is meant by "adding corners"? I don't recognise this term at all. This is to do angle points, can we make the terminology consistent here. Also if you drag a table onto an ERD does it save automatically. We need to confirm this as I would not expect it to as the same does not happen in analysis models.

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. It's not any attribute to any attribute. We need to add a note that dragging a UID onto a header will auto create a foreign key.

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


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.

To select multiple tables, draw a square around them.

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.
  • Should we add the concept of 1:many and many:1 here?

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.

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

  1. Click on a relationship line to add an angle point, which appears as a blue dot.
  2. Move the mouse pointer over the blue dot. It changes to a four-way arrow to indicate you can drag.
  3. 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

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Basic Settings

FieldDescription
Name

The name for the ERD.

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How PhixFlow Manages Different Relationship Drags

DragRelationship line

Foreign key type

If PhixFlow does any automatic changing of types, then record them here

From table1To table2
primary keyattribute

table1.primarykey → table2.attribute
one → many

Table has no records:  

Table has records: 21052021 PhixFlow creates relationships with types that don't match

attributeprimary key

table2.primarykey → table1.attribute
one → many

primary keyprimary keytable1.primarykey → table2.primarykey
one → one 		21052021 should this work? No
attributeattribute

if table1 has no primary key: PhixFlow makes the table1.attribute the primary key

if table 1 has a primary key: relationship is from table1.primarykey  instead of from table1.attribute.



ERD Toolbar we haven't defined this in our terminology document but we have been calling it the In Context Toolbar to ensure there is no ambiguity with any other options.

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

OptionDescription
Create
CreateDrag this icon onto the canvas to create a table.
ScreenCreates a new screen for the selected table.
List
TablesClick to see a list available tables.
ScreensClick to see a list available screens.
 Canvas
SaveSave 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.

PropertiesOpen 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.

ForwardFor 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 
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  • right-click anywhere in the table.
OptionRename 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 AttributesHide attributesCollapse the table so that it only shows the table name, primary key and any foreign keys. Other attributes are hidden.
Show AttributesShow attributesExpand the table to show all the attributes
Parmanently DeleteDelete everywhereDDelete the selected item(s) from the ERD and from everywhere it is used.