Insert excerpt

	_Banners
	_Banners
name	ERD
nopanel	true

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 tables. The lines connecting the Tables show tables show the Relationships relationships between them.

Image Added

The following illustration shows how an ERD represents a table.

Image RemovedImage Added

The table has a list of attributes, which represent the different pieces of data you want to record. For example, the Student table 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 its details including the data type. For example, IntakeYear is set to Date. It 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 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 Rollback Recordsets; 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 table, PhixFlow adds an attribute called UID (short for Unique IDentifier) and configures it as follows:

as the table's primary key.
as an integer.
to automatically create a unique number for every record in a table.

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

Insert excerpt

	_uid
	_uid
nopanel	true

Display Name
Anchor
display-name
display-name

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 sense to a humanperson. 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 will be shown display name is shown in place of the Primary Key primary key when displayed on a Viewview or screen. Display Names names do not need to be unique and should be something user-friendly.

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

a UID, for example 1490

or 1550, and

.
a Name, for example Mathematics.

To help users make sense of this PhixFlow will display the department's Name, when when any relational When any view makes reference to the SchoolDept using it's Primary Key. See Relational Views for more informationprimary key, PhixFlow displays the department name, not its number; see Using Relational Views. The configuration is shown below:

SchoolDept SchoolDept
primary key Primary Key Display Name

Relationships and Foreign

Keys

Keys
Anchor
relationships
relationships

Tables in PhixFlow are relational, which means information in one table can be related to, or linked to, information to information in another table. The key benefit is you can access data in many different 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 tables: the SchoolDept.DeptID to the Teacher.Department:.

Image RemovedImage Added

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 we you only need to store the School DeptID against a teacher , but we have access to to be able to access all of the SchoolDept details such as Name.

When you create a relationship from a primary key to an attribute, PhixFlow automatically sets the attribute to be a foreign key. Foreign keys must have the same data type and properties as the corresponding Primary Keyprimary key. For example, in the illustration above, the Teacher.Department attribute contains the same Data Type data type as SchoolDept.DeptID; 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 instance 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 table showing Teacher.Department will have data such as Science, rather than an ID like1490.

One-to-many and Many-to-one

PhixFlow 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 table that has foreign key attributes from each of the 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 table called CourseAttendee. Notice that CourseAttendee does not need a unique identifier.

Image Modified

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

Using ERDs in Views

ERD's are important because the tables, 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 table rows and columns.

The concept for a view is described below:

Start with a specific table, which is the base table for the view.
Select the attributes from the base table that you want to be the columns in the grid.
From related table, select other attributes to add more columns to the grid.
PhixFlow joins the related tables via their relationships.
Under-the-hood this is done using a direct SQL join.

Tip

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

the base table
tables related via a many:1 relationship.

Image Removed

TODO we may not get this

Why You Cannot Show Data from 1:many Attributes

If you add an attribute from a table that is related to the base table 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.

Creating PhixFlow Tables From Existing Data

You can create table in an ERD, but if you already have data, PhixFlow can create tables from it.

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

Adding Content to an ERD

I have Excel dataFirst use an analysis model to connect to your data. PhixFlow can read the data structures to create tables. When you run analysis on the model, PhixFlow loads the data records.Adding Content to an ERDI have data outside of PhixFlowAPI, Database and other forms of data can be imported using an analysis model. This will create tables which can then be added to your ERD by clicking Insert excerpt_tableOnly_tableOnlynopaneltrue on the toolbar and dragging the items in.Importing DataI have data in PhixFlow alreadyIn the ERD toolbar, click Insert excerpt_table_list_table_listnopaneltrue to display a list of all the tables. Drag tables into the ERD and then add the relationships.Adding Content to an ERD

Displaying ERD Data

Viewing ERD Data
Anchor
view
view

Insert excerpt

	_view_records
	_view_records
nopanel	true

HTML Comment

hidden	true

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 table that have a matching key value. This is why the base table 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 table to a foreign key in a related table. 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.

Image Removed

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.