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Overview

PhixFlow ERDs define the logical structure of the data in your application.

The following example shows an ERD for a school. A school has entities, for example: departments, teachers, students, classrooms and so on. All these entities are represented as stream tables. The lines connecting the Tables show tables show the Relationships relationships between them.

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The following illustration shows how an ERD represents a table.

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The table has a list of attributes, which represent the different pieces of data you want to record. For example, the Student stream in the ERD above has the attributes: UID, Address, IntakeYear and Name.

Attributes are configured with a data type and associated properties, for example the Name and Address attributes are "String" typesa data type and associated properties; see Understanding Data Types. For example the Address attribute is a String which has an associated length. To change the attribute to reflect the nature of your data, click on the attribute's name to open it's properties, here you can set the type. For example, IntakeYear is set to Date. It is and edit its properties.

It is important to set the correct data type and type and properties before loading records into a table, as you cannot change the data type once the data type once the table stream contains records. If you do have data and want to change the type you will need to add a new attribute or clear your data; see Clearing and Loading Data in an ERD.

You can create tables in an ERD manually, but if you already have data, PhixFlow can automatically create tables from it; see Adding Content to an ERD.

Primary Keys and UIDs

PhixFlow expects every table to have a special attribute called a primary key, which uniquely identifies each record. For example, teachers have a UID as the primary key. This is because they can have the same first or family name, or even both, so these attributes cannot be a primary key. When you create a streamtable, PhixFlow adds an attribute called UID (short for Unique IDentifier) and configures it as follows:

as the table's primary key.
If you look at the School ERD example above, you can see that every stream has an attribute called UID, and that it has the primary key icon next to it.
as an integer; see the SchoolDept primary key properties on the right.
to automatically create a unique number for every record in a table.

This means PhixFlow can ensure all the UIDs have unique values.

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Display Name
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Typically a Primary primary key is not user-friendly and you do not want to display it. Instead, you want to display something that makes more suitable for a human, for sense to a person. For this reason, when you create a table, PhixFlow automatically adds an attribute called Name and ticks the its Display Name property. The Display Name does display name is shown in place of the primary key when displayed on a view or screen. Display names do not need to be unique and should be something more user-friendly.

Lets Let's look at the following example. For the SchoolDept table, PhixFlow has created:The SchoolDept and

a UID

setup by PhixFlow

, for example 1490

or 1550. To help users make sense of this PhixFlow will display the department name, such as Arts or Science

.
a Name, for example Mathematics.

When any view makes reference to the SchoolDept using it's primary key, PhixFlow displays the department name, not its number; see Using Relational Views. The configuration is shown below:

SchoolDept SchoolDept
primary key Primary Key Name Display Name

Relationships and Foreign

Keys

Keys
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Tables in PhixFlow are relational., which means you means information in one table can be related to information in another table. The key benefit is you can access data in many different ways tables without needing to duplicate datait.

A foreign key is an attribute in one table, that refers to the primary key in another table.

In the an ERD you can connect tables by drawing a line, called a relationship between them. For For example, the Teacher table needs to have the name of a department. The ERD below represents shows this relationships relationship using a line that joins the SchoolDept table to the Teacher table:Image RemovedSchoolDept.DeptID to Teacher.Department.

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

When you create a relationship from a primary key to an attribute, PhixFlow automatically sets the attribute to be a foreign key. Foreign keys can have different names to the primary key, but they must have the same data type and properties as the corresponding primary key. For example, in the illustration above, the Teacher.Department attribute contains the same values data type as SchoolDept.UID; as shown in the attribute properties on the right. However, in the Teacher stream there may be more than one instance of a valueDeptID; see Understanding Data Types.

The foreign key represents the many side and the primary key the one side. This means that SchoolDept.DeptID is unique, there is only one record containing this unique information. The Teacher.Department, can have one or more instances of a value of DeptID. For example, the Maths Department UID could occur 10 times, once for each of the 10 maths teachers.Although the relationship is between the primary key and a foreign key, when the foreign key is included in a screen, PhixFlow shows the attribute that has Display Name selected, which is the Name attribute by default. This gives the user a the meaningful string, rather than the primary key's identifier. For example, a stream showing Teacher.Department will have data such as Arts or Science, rather than an ID like1490.

Attribute properties for:

ClassRoom
Department

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One-to-many and Many-to-one

PhixFlow always draws a relationship line between a primary key and a foreign key. This represents a 1:many relationship. The "many" end of the line has several lines. one-to-many relationship. For example, one teacher runs many courses. A many:1 A many-to-one relationship is implied when you read a relationship in the opposite direction. For example, a department has many teachers, and several teachers work for one department.

Many

-to-

:many

To create a many-to-many relationship, you need an intermediate stream table that has foreign key attributes from each of the streams tables you want to have a relationship. For example, many students take many courses. A many-to-many relationship is shown below, using the intermediate stream table called CourseAttendee. Notice that CourseAttendee does not need a unique identifier.

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A course is attended by many students
A student takes many courses.

Using ERDs in Views

ERD's are important because the streams, attributes and relationships define the logical structure of the data that your application uses. PhixFlow displays this data to application users via views. Most commonly this will be a grid view, which displays data in rows and columns.

The concept for a view is described below and illustrated on the right:

Start with a specific stream, which is the base stream for the view.

Select the attributes from the base stream that you want to be the columns in the grid.

From related streams, select other attributes to add more columns to the grid.

Note
PhixFlow can only display data from a related primary key.

PhixFlow joins the related streams via their relationships.
Under-the-hood this is done using a direct SQL join.

Link to how to create a view. I feel as though this needs the attribute selector

Tip

The attributes that will display data on a grid view are those in:

the base stream
streams related via a many:1 relationship.

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Why You Cannot Show Data from 1:many Attributes

If you add an attribute from a stream that is related to the base stream via a 1:many relationship, PhixFlow does not show any data in the grid rows. This is because there may be many values, which cannot be displayed in a single cell of the grid.

Tip
In a future release, it will be possible to aggregate numerical data from a 1:many relationship.

I am here - the following section should probably go .

Displaying Names Not Identifiers

Tip
In a future release, foreign keys will show the display name rather than the primary key identifier.

Streams are related via primary keys. If a stream has a foreign key attribute and you use it in a grid view, the column displays the identifier. You can see this in the Teacher column below.

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This can be put into the compiling views bit maybe

When creating the view, you need to choose a stream to be the base stream. Your choice depends on the records that you want to show, as it is the base stream's records that are displayed. In this case I want the records from the course stream, in which there is one record for each course, so when I create the view I start with this stream.

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The left of the Attribute Selector / View Editor window lists related streams. By selecting the Teacher stream, I can add the Department attribute to the grid view.

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For details of creating views and using the attribute selector see Understanding Data Views and Showing Data on a Screen.

Editing Data in a View

When you create a view that includes attributes from related streams, only data from the base stream is editable. For example, using the view in the example above, you could create a form to add a new course, with fields for:

Department
Course
Classroom
Teacher.

However, as the Department attribute is not present in the base Course stream, you cannot add the department information via the form.

Creating PhixFlow Streams From Existing Data

You can create streams in an ERD, but this is time consuming. If you already have data, PhixFlow can create streams from it.

Starting PointEasiest MethodSeeI have no dataDefine the streams, attributes and their relationships in the ERD.
You will need to add records to the streams.

Adding Content to an ERD

I have data but it's not in PhixFlowFirst use an analysis model to connect to your data. PhixFlow can read the data structures to create streams. When you run analysis on the model, PhixFlow loads the data records.Data Import ScenariosI have data in PhixFlow alreadyIn the ERD toolbar, click Insert excerpt_table_list_table_listnopaneltrue to display a list of all the streams. Drag streams into the ERD and then add the relationships.Adding Content to an ERD

Viewing ERD Data
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9.0.0 todo - technical questions outstanding

The Course grid has duplicate records, and I don't understand why.
combination of columns - Its an SQL Join. Phixflow finds ALL the records in the related stream that have a matching key value. This is why the base stream should have a many to one relationships to the related stream. This will only have ONE unique record - the primary key. For each record in the base stream, PhixFlow goes to the join column, finds the ID in the related stream and fetches back the appropriate attribute. This is a single value.
Do not try to connect from your primary key in your base stream to a foreign key in a related stream . In this case PhixFlow will find multiple records. It cannot display multiple records in the single cell available.
For the Views page -When aggregation comes in, link to Aggregating Data
Editability of fields: ask Gary about: "and only then if you haven't followed a one-to-many relationship." I think this might be the same issue as illustrated by the grids in 4.
explain why one-to-many / many-to-one are important. You might want to include worked examples showing the data you will get if you build a view starting with
- Teacher
- SchoolDept

So I created the grids and see blank columns. I think this relates to aggregation.

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What about views other than grids

cards

fields

graphs - line, vertical and horizontal bar

For Creating PhixFlow Streams from Existing Data

Streams line...

I have data in Excel files

Drag the Excel files directly into an ERD. PhixFlow loads the data and adds the stream to the ERD.

In the ERD, you then add the relationships between streams.

Remember to link to doc that covers XD flow 4.10

See Creating Dashboards and Reports.