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

Creating Tables in an ERD

Open an Existing ERD

In the repository, find ERD.

Create a New ERD

Add an Existing Stream

Drag and Drop Import: Create a New Table using Excel or CSV

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1. Drag a CSV or Excel file directly onto an ERD canvas.
2. PhixFlow creates a table automatically based on the information in the file.

This topic is also covered in the ERD Fundamentals video course; see Entity Relationship Diagrams.

Create a New Table 

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1. Drag 

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     from the toolbar into the diagram.
2. In the pop-uppopup, enter a name , for example "Customer", and click Insert excerpt_dialog_finish_dialog_finishnopaneltruethat reflects what the table will represent. For example Customer.
3. PhixFlow opens the properties tab for the new stream on the right table and adds the stream table to the canvas.
   The table header displays the its name entered in step 2.PhixFlow automatically adds 2 two attributes:

1. • UID - PhixFlow requires , a primary key that is a unique identifier and primary key for each streamrecord.
   • 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,  a display name that is shown instead of the numeric UID in a view or form.
2. To add attributes to the streamtable:
   1. In the streamtable, click 

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      . 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 AttributesAttribute. 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 

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       to save the attribute properties.
3. PhixFlow adds the attribute to the stream in the ERD.the table in the ERD.

Add an Existing Table

1. In the toolbar, click 

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   .
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 Relationships

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

To create a relationship, click

1. Click-drag from one attribute name to another.
   

1. One of the attributes must be a primary key.
2. PhixFlow highlights the attribute when your mouse pointer is over it. 
3. When the destination attribute is highlighted, release the click.

Relationships

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

Relationship Restrictions

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 streamthe 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.

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 

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

• Image RemovedShow many to one relations Todo Todo-Fiona - check icons 

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  Image RemovedShow one to many relations Todo-Fiona - check icons 

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PhixFlow adds the related streams tables to your ERD. 

To keep the related streams tables in your ERD, in the toolbar, click 

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

Saving ERDs

Changes to streams, attributes and relationships are automatically saved. However, to keep any Any changes you make to the layout of a diagram, such as moving streams or adding angle points to relationships, remember to click  Insert excerpt_save_savenopaneltrue 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:

on the ERD canvas are automatically saved. 

Accessing Properties

To access properties for:

• the ERD: in the canvas toolbar click

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• for a streamtables: in the ERD, click on the stream the table header or right-click to open the pop-up popup menu and select 

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• for an attributeattributes: in the streamtable, click on an attributefor 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.

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• 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. 

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

1. Click on a relationship line to add an angle point, which appears as a blue dot; see the screenshot on the left.
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; see the screenshot on the right.

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

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

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pane on the right.