The table has a list of attributes, which represent the different 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 labelled as "String". To make it easy to create an attribute, PhixFlow sets the type to String by default. To change the attribute to reflect the nature of your data, click on the attribute name to open it's properties, where you can set the type. For example, IntakeYear is set to Date. It is important to set the correct data type and properties before loading records into a table, as you cannot change the data type once the table contains records.
| Tip |
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If you have data outside of PhixFlow, we recommend you use a PhixFlow analysis model to connect to your data source(s) and use them to create your table structure; see Load Data. This means PhixFlow can create tables and can determine the data type for the attributes. |
Identifying an Attribute
This help page refers to an attribute using the form table.attribute, for example: Teacher.Name, Student.Name or SchoolDept.Name.
Primary Keys and UIDs
PhixFlow expects every table to have a special attribute, called it's primary key. The primary key contains a unique value for every record. For example, several teachers 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 automatically adds an attribute called UID (short for Unique IDentifier) and configures it:
- as the table's
primary key.
If you look at the School ERD example above, you can see that every table 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 its own UIDs have unique values.
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Where your table's primary key is a UID, you usually do not want to show it to the user in data tables. For example the SchoolDept.UID will be a number, for example 1490 or 1550. Application users want to see the department name, such as Arts or Science. For this reason, when you create a table, PhixFlow automatically adds an attribute called Name and ticks its Display Name property, as shown for the SchoolDept.Name attribute on the right.
Attribute properties for:
SchoolDept SchoolDept
primary key Name
Relationships and Foreign Keys
Tables in PhixFlow are relational. This means you can access data in many different ways without:
- having to duplicate data
- reorganizing the database tables themselves.
In the ERD you can connect tables by drawing a line, called a relationship. This tells PhixFlow that the two tables are related. For example, both the Teacher and ClassRoom tables need to have the name of a department. The ERD represents these relationships using a line that joins the SchoolDept table to the ClassRoom table and to the Teacher table ( as shown in screenshot below).
When you create screens that show data, PhixFlow uses the relationships from the ERD to provide options for displaying data from related attributes in the same grid, form, card, graph or chart.
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. For example in the illustration above, the Teacher.Department attribute contains the same values as SchoolDept.UID; as shown in the attribute properties on the right. However, in the Teacher table there may be more than one instance of a value. 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 Arts or Science, rather than an ID like1490.
Attribute properties for:
ClassRoom
Department
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. For example, one teacher runs many courses. A many:1 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.
Come back and add something after doing relational views and aggregation: Gary says: This doesn't really 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 and a similar view starting with SchoolDept. You should also cover the importance of the 'Primary' table (the starting table in a joined view, in particular that you will only be able to edit fields that came from the Primary table, and only then if you haven't followed a one-to-many relationship.
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.
- A course is attended by many students
- A student takes many courses.
Show in a relational view with worked examples in a table e.g using data in tables Sketch something up and use mockaroo and powerpoint for images: Again, I think this would benefit from a worked example showing that you get records with combinations of records from each table.
Why ERDs are Important
The ERD's tables, attributes and relationships define the logical structure of the data that your application uses.
Just that it relates to views and views talk about how you access them - keep this simple - show an example with real data....When you are creating views to display data in your application, you may want to combine attributes from different tables into one view. For example, your application might want to show:
- Course Name
- Department Name
- Teacher Name
- Number of Students
Each of these attributes comes from a different table. The relationships that you create between tables in an ERD make it possible for PhixFlow to create views using attributes from different tables. For example:
Show an example with the Attribute Selector and a view - something more visual
Creating PhixFlow Tables From Existing Data
You can create tables in an ERD, but this is time consuming. If you already have data, PhixFlow can create tables from it.
| Starting Point | Easiest Method | See | ||||||||
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| I have no data | Define the tables, attributes and their relationships in the ERD. You will need to add records to the tables. | Defining Data Structures using ERDs ??How | ||||||||
| I have data in Excel files | Drag the Excel files directly into an ERD. PhixFlow loads the data and adds the table to the ERD. In the ERD, you then add the relationships between tables. | ??Link to doc on XD flow 4.10 | ||||||||
| I have data but it's not in PhixFlow | First 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. | Load Data | ||||||||
| I have data in PhixFlow already | In the ERD toolbar, click
| Defining Data Structures using ERDs |
If you are working with tables that have records, to see the records:
- In the ERD, click on a table to open its properties.
- In the properties toolbar, click
.Insert excerpt _more_options _more_options nopanel true - Select
.Insert excerpt _view_show _view_show nopanel true - PhixFlow displays a the default grid view, listing all the data records.