ERD Fundamentals

Overview

Entity Relationship Diagrams (ERDs) define the structure of the data in your application. "Entities" are displayed as tables and represent the "things" in the world that you want to show as data.

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Opening and Creating ERDs

• On your application's home page, click

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   to list the existing ERDs.
  • Alternatively, click

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     from the header bar. 
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• To create a new ERD, click the 

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  button.
• To open an existing ERD, double-click it.

ERD Layout

Here is a simplified view of the ERD editor:

1. The Toolbar provides ERD specific options, such as displaying the available tables that can be added to your ERD and options for creating a new screen for your data.
2. The Repository browser, can list all of the available tables in your application and any associated packages. Select Tables from the toolbar to display this area. 
3. The Canvas area is where the ERD is configured. Tables can be added by:
   1. Dragging a Table from the toolbar onto the canvas.
   2. Clicking Tables from the toolbar and dragging a table from the repository onto the canvas.
   3. Excel documents and CSVs can be dragged directly onto the canvas and will be imported automatically.
4. The Tables and Relationships, are displayed on the canvas. A Table Shows all of the attributes it contains within it and their data type. A Relationship between two tables is displayed as a line connecting the primary key of one table to a foreign key of a second table. This is discussed in more detail in Relationship.

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Overview

PhixFlow Entity Relationship Diagrams (ERDs) define the logical structure of the data in your application. "Entities" represent the things in the world that you want to represent as data.

The following example shows an ERD for a school. Here the school has entities: departments, teachers, students, classrooms

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Tables

A table is where your data is stored for your application. Click on the image below to enlarge it.

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Attributes

Attributes represent the different pieces of data recorded in the table, and can be thought of as column headers on a spreadsheet.

• Attributes are configured with a data type (e.g. string, integer, true/false) and properties. To change these, click on the attribute's name. See Understanding Data Types.

Primary Keys

• When you create a new table, PhixFlow adds an attribute called UID (Unique IDentifier) and configures it as follows:

  • the table's Primary Key
  • an integer
  • automatically creates a unique number for every record in the table
• If your data already has a unique attribute, you can use this as the Primary Key by right-clicking and selecting Make Primary Key. 
  • On the example image above, the Employees table has the attribute EmployeeID as the Primary Key. This is because teachers may have the same first and/or surname, so these attributes cannot be guaranteed to be unique and therefore cannot be a Primary Key.

Secondary Keys

• When creating relationships on the ERD, one attribute in the relation must be either a Primary Key or a Secondary Key

Example: In a student records table, if a student ID is the primary key, a student's email address or phone number could be a secondary key. This allows data to be retrieved using these attributes even if the student ID is not known.

Foreign Keys

• Foreign Keys must have the same data type as the corresponding Primary Key or Secondary Key. For example, both must be strings and of the same length.

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Display Names 

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DisplayName DisplayName

Display Names are special attributes which are displayed instead of a Foreign Key, as they make more sense to a human.

• When you create a new table, PhixFlow adds an attribute called Name and configures it as the Display Name.
  • This is then shown in place of the Foreign Key when displayed on a screen as part of a relational view, see Using Relational Views. Display Names do not need to be unique and should be user-friendly.
• If your data already has an attribute you want to use as the Display Name, right-click it and select Make Display Name. 

Validation

Validation is applied to table attributes and determines the criteria an attribute must satisfy in order to be considered valid. For example, the attribute is mandatory, must contain a minimum number of characters or must adhere to a specific pattern. Validation, added to a table attribute, will be applied wherever that attribute is updated, such as when saving data on an input screen. See Adding Validation to Table Attributes.

Indexing

Indexes are applied to attributes on a table and help improve the speed of data retrieval when handling large data sets. See Indexing.

Relationships Between Tables 

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relationships relationships

For full information on table relationships, including multi-hop relationships, see Understanding Table Relationships.

Working in an ERD

You can add tables in an ERD manually. See Adding Data and Tables to an ERD.

• Create a new table by dragging 

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   from the toolbar onto the canvas.
• Add an Excel spreadsheet or CSV file by dragging it onto the canvas. PhixFlow imports the data and creates a new table. Note, the expected format is the header is the first row followed by the data. If your data is in a different format, this is supported, see Importing Data from Excel (Advanced).
• Add an existing table by clicking 

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   in the toolbar. The available tables are listed in the Repository and can be dragged onto the canvas. 
• If you have data in an external source such as database and wish to add this data, it will first need to be imported. See Importing Data.

View Table Data 

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To view the data in a table, click 

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Create a Screen from a Table

Select 

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Multiple ERDs

The same table can appear on multiple ERDs.

ERD Example

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Create an ERD

1. Click the ERD link on your application's home page.
2. This lists all existing ERD diagrams and provides an Add button for creating new ERDs.

Open Existing ERD

1. Click the ERD link on your application's home page.
2. This lists all existing ERD diagrams.
3. Double click any item to open it.

Already Have Data?

If you have data that you wish to import into PhixFlow, such as a database or csv, you will need to use an Analysis model to import it. See Importing Data and Importing Data Through an API.

Analysis Models will allow you to configure connectors to access your existing data sources and store the data as tables in PhixFlow's own database. You can also set up more bulk processes to manipulate large volumes of data before it is presented to your users; see Analysis Model Properties.

What Next?

Understanding ERDs covers ERDs in more depth to help you design your own ERDs and views to display your data.

What's Next?

The PhixFlow Fundamentals course provides a practical guide to using PhixFlow, including setting up ERDs. 

Already started PhixFlow Fundamentals?

Return to ERD Fundamentals

Further Reading