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Overview

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

The ERD Window

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 window:

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  • The toolbar provides ERD specific options, such as displaying the available data tables that you can add to your ERD and creating a new screen for your data. 

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    1. Toolbar: This contains ERD-specific options to add data to the ERD and move tables on the canvas.
    2. Repository: On the toolbar, click
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    . The main part of the window is the canvas, where you create the ERD.To add a new table, from the toolbar, drag the  Insert excerpt_tables_tablesnopaneltrue icon onto the canvas.To add an existing table, on the toolbar, click  Insert excerpt_tables_tablesnopaneltrue. PhixFlow lists the available tables in the repository. Drag a table from the repository onto the canvas. 
  • To add an Excel or CSV spreadsheet, drag it directly onto the canvas. PhixFlow imports the data and uses it to create a new table.

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    Table Relationships

    1. A table is represented as a box, containing a list of all of the attributes it contains and their associated data type.
    2. A line connecting tables represents the relationship between them. The line connects the primary key of one table to a foreign key in a different table; see Relationship.

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    ERD Example

    The following example shows an ERD for a school. Here the school has entities: departments, teachers, students, classrooms and so on. All these entities are represented as tables and the lines connecting them show their relationships to one another. We can see from this diagram that a School Department has many Classrooms and Teachers. This example is covered in detail in Understanding ERDs.

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    Creating an ERD and Opening an Existing ERD

    On your application's home page, click Insert excerpt_erd_erdnopaneltrue to list the existing ERDs.Alternatively, click Insert excerpt_erd_erdnopaneltrue from the header bar. On the Entity Relationship Diagrams page:Click the  Insert excerpt_add_addnopaneltrue button to create a new ERD.
  • Alternatively, double-click any existing ERD to open it.

    • Already Have Data?

    If you have data to import into PhixFlow, such as a database or API, use an Analysis Model to import it. This allows you to configure connectors to access your existing data and store the data as tables in PhixFlow's own database. See Importing Data and Importing Data Through an API.

    You can also use an Analysis Model to set up bulk processes to manipulate large volumes of data before it is presented to your users. See Analysis Models for Batch Processing Data.

    What's Next?

    Understanding ERDs covers ERDs in more depth to help you design your own ERDs and views to display your data.
    1. . These can be dragged and dropped onto the canvas.
    2. Canvas: This is where you create and modify your ERD.
    3. Table: This is represented as a box, containing a list of all of the attributes within the data and their associated data type (e.g. string). 
    4. Relationship: This is represented as a line connecting the tables.
    5. Options: View the data in the table by clicking 
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       or show all table options by clicking 
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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

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    s are special attributes which uniquely identify each record. 

    • 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

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    s are attributes that index records and do not have to be unique.  

    • 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

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    s are attributes in one table that relate to the Primary Key or Secondary Key in another table.

    • 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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    When a relationship is created by dragging a Primary Key or Secondary Key from one table onto the attribute of another table, PhixFlow sets this attribute to be a Foreign Key.

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    Display Names 
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    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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    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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     from the header as illustrated below. Different views can be created and will also be made available from this option, see Creating Dashboards and Reports (Charts and Graphs).

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    Create a Screen from a Table

    Select 

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     from the table options and click Create Screen. See Creating a Screen from an ERD Table.

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    Multiple ERDs

    The same table can appear on multiple ERDs.

    ERD Example

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    The below example is an ERD for a school.

    A school has entities, for example: departments (SchoolDept), teachers, students, class rooms, and so on. All these entities are represented as tables. The lines connecting the tables show the relationships between them. We can see from this diagram that a Departments (SchoolDept) has many Classrooms and Teachers.

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    In the Teacher table, Department is the Foreign Key and contains the same data type as the Primary Key, UID, in the SchoolDept table. 

    The Foreign Key represents the many side and the Primary Key the one side. This means that SchoolDept.UID is unique and there is only one record containing this unique information. Teacher.Department can have one or more instances of a value of UID. For example, the Maths Department UID could occur 10 times, once for each of the 10 maths teachers.

    When you create screens that show data, PhixFlow uses the relationships defined in the ERD to provide options for displaying data from related attributes in the same grid, form, card, graph or chart. This means you only need to store the School DeptID against a teacher to be able to access all of the SchoolDept details. See Displaying Data (Views).

    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

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