Creating and Managing Lookup Tables in ER Diagrams

Step 1: Setting Up the Major Entity

• Open the example Enrollment project. You can download it here: Enrollment (ER Diagram)
• Create a new entity:
• Click on the toolbox and then on the diagram canvas to add a new entity.
• Name this entity 'Major'.
• Add two attributes to the Major entity:
• 'ID' - and set it as a primary key (right-click on the attribute and choose Primary Key from the context menu)
• 'Name' and choose varchar type (right-click on the attribute and choose Change Type and varchar from the context menu)

Step 2: Modifying the Student Entity

• Change Major attribute to MajorID:
• In the 'Student' entity, rename the 'Major' attribute to 'MajorID'.
• This change creates a more explicit relationship between the 'Student' and 'Major' entities.

Step 3: Connecting Entities and Handling Data Types

• Create a relationship:
• Choose the '1 to 1..n' relationship from the toolbox
• Draw a relationship line from the 'Student' entity to the 'Major' entity.
• Resolve data type mismatches:
• If prompted by a warning about differing data types between 'ID' and 'MajorID', choose the appropriate option (int) to resolve this.

Step 4: Populating the Major Lookup Table

• Add data to Major entity:
• Select the 'Major' entity.
• Click on the 'Add Data Row' button in the context bar.
• Enter values such as 'Computer Science', 'Biology', 'History', and 'Psychology' with appropriate IDs (e.g. 1,2,3)

Step 5: Managing Data Visibility

• Hide data in the ER diagram:
• Right-click on the 'Major' entity.
• Navigate to 'Show Parts' in the context menu.
• Uncheck 'Data' to hide data from being displayed in the diagram.