todo better image Doc simple 1
Entities are the data tables that your application has or will have.
First create your "entities"
table, attributes
Set up relationships
e.g. invoice is for a customer. Tell PhixFlow "customer name" is connected via customer ID
This creates arelation and marks it as a forign key - with glyph to show it.
Its important to understand that the connection is there for other stuff - for creating views that combing information from multiple streams so that you can
If you wanted a screen with cust info at top and a list of depts it would need to know how to do this.
The line means go and find it from the other table and can then find the matching attribute and preport the records (by following the line). (show it as an animation
Turn this into a simple explanation with a sequence
Start with tables and attribures
Explain primary keys
Explain relations and foriegn keys.
| Key concepts | ||||
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| Entity-Relationship Diagram | PhixFlow Relationship Diagram | Examples | ||
| A database table represents a thing or entity. | A table (was stream) represents a thing or entity.
| Entities:
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| A database table has columns for different aspects of the data. The column headers are called data attributes. | The table in a relationship diagram has a list of attributes. | Employee attributes:
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PhixFlow automatically generates a unique identifier, UID. (Integer, sequence) attribute that has unique values. The unique attribute is the primary key. | Primary Keys
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Improve When the data from one stream's primary key also appears in a different stream, it is a foreign key. This gets set automatically when you connect up an ERD todo update using UX terminology Use an example to show that the things are linked by relationship and that the data is connected and may not have the same name (can be a later concept) Tell PhixFlow there is a relationship | Employee attributes:
Department attributes
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Tables or attributes can have various relationships to each other
| Attributes can have relationships. On the diagram the relationship is shown as an arrow. Relationships can only be one-to-many, from primary key to foreign key. When you are designing screens, you can create views to display attributes from a table AND from tables with a direct relationship. | Relationships
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| Note |
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We recommend that a primary key attribute should be an integer, because PhixFlow can automatically generate a unique integer value for each new data record. |
More About Relationships
The name for the relationship should reflect its direction. For example:
- either company → employs → people
- or people→ work for → company
- but not company → work for → people
PhixFlow imposes no restrictions on the names for relationships, Between two tables with multiple relations, each connection must have a unique name.
Many-to-Many Relationships
You can show a many-to-many relationship by using an intermediate stream. This stream has attributes that are foreign keys from the two streams you want to connect, with a one-to-many relationship into the foreign keys. For example
- A customer buys many products
- And a product can be bought by many customers
- The intermediate stream is a Customer Purchase Record, which has both the CustomerID and ProductID as foreign keys.
Example
In a relationship diagram, a stream and its attributes are displayed as a box. You can expand or collapse the box using the icon in the top left. PhixFlow shows all the attributes when the stream is expanded, and only the primary and foreign keys when it is collapsed.
todo Update labels with UX terminology Departments needs to go and there is not foriegn key here...
The following diagram shows some relationships between streams that represent a company, its employees and departments, the products it makes and the customers who buy them.
All of the plural foreign keys are wrong
Limitations - single hop relationships. You cannot go Project → Opportunity → Statuses at the moment. You need to go from one table
- Project → Opportunity
- Project → statuses
The company "contains" many departments. An employee "works in" a department, and a department can have many team members. In this company, the department "makes" several products, which "ship to" many customers.
Relationship diagrams are useful because you can design relational views that use data from multiple streams. For example, you might want a view that shows the employee details by department. This will display data from the Employee stream and the Department stream. The relationship diagram shows these are connected by the DepartmentID attribute.
Relationship Diagrams in the Repository
When you create a relationship diagram, you start in the repository. Find the
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As you draw the diagram, PhixFlow adds items to the repository:
- a stream for each table; see
- a stream attributes for each attribute. These are nested under the stream in the repository.
- a relation for each relationship.
todo Draft image needs improving
Related things
Relationship diagrams do not show changes over time, responsibilities or processes. To represent this type of information, use a Workflow Diagram.
Relationship Diagrams and Relational Views
Relationship diagrams underpin the ability to create views that combine data from different streams.
When you create a GUI screen for an application, a view can display the data records for selected attributes using a Stream View. This can be a grid (table), a graph or a chart. If a table has no relationships to other tables, PhixFlow can only show attributes and records from that stream.
When a table has a direct relationship to other tables in a relationship diagram, PhixFlow can display the data for the attributes from the related tables.
For example, with the following relationship diagram, you can create a view based on the "Departement" stream that shows
- Company name from table Company
- Department names from table Department
- Product category and Status from table Products
todo better diagram and example
Toolbar
| Anchor | ||||
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| Zoom out to see more of the diagram, with smaller text. | ||||||||
| Zoom in to see a smaller area of the diagram, with larger text. | ||||||||
| Organise selected objects in a grid. | ||||||||
| Align all selected objects left. | ||||||||
| Align all selected objects right. | ||||||||
| Align all selected objects to top. | ||||||||
| Align all selected objects to bottom. | ||||||||
| Either drag into the diagram to add a stream or click to open the list of streams in the repository and drag a stream in from the repository list. | ||||||||
| Save the relationship diagram. | ||||||||
| Refresh the diagram, for example to show changes to an attributes Primary Key or Foreign Key properties. | ||||||||
| Opens this help page for relationship diagrams. |
Context Menu
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