Create a diagram with Chen's database notation

Create the diagram and entities

1. In Visio, on the File menu, select New > Software, and then select Chen's Database Notation.

2. Choose either Metric Units or US Units, and select Create.

3. From the Chen's Database Notation stencil, drag an Entity shape onto the drawing page.

4. Drag another Entity shape onto the drawing page to create a second entity.

5. Drag a Relationship Connector shape onto the drawing page. Hover the shape over one of the entities, and release the mouse button. The connector is now connected to that entity. Drag the other end of the connector to the other entity to glue it there. 

6. Optionally, you may right-clicking the connector and select Show Multiplicity.

7. Drag a Relationship and place it on top of the connector line. To indicate that the relationship is optional, right-click it and select Set Identifying.

8. To add an attribute to an entity, drag the Attribute from the Shapes pane toward the entity. When the connecting line is over the entity, a green highlight line encloses the entity, indicating that the attribute will be glued to the entity when you release the mouse button. 

9. Right-click the attribute and choose from the options at the top of the menu:

   • Set Primary Key: An attribute that uniquely identifies a particular entity.

   • Set Multivalued Attribute: An attribute that can have many values—that is, there are many distinct values entered for it in the same column of the table. 

   • Set Derived Attribute: An attribute whose value is calculated, or derived, from other attributes. A derived attribute may or may not be physically stored in the database.

   • Set Required: A required attribute must have a value in it, while an optional attribute may not have a value in it and can be left blank.

Create the diagram and entities

1. Open Visio for the web and search for Chen's.

2. Select the Chen's Database Notation diagram.

3. In the dialog box, select either Metric Units or US Units.

4. Select Create.

5. The diagram opens. You should see the Shapes window next to the diagram. If you don’t see it, go to View > Task Panes and make sure that Shapes is selected. If you still don’t see it, click the Expand the Shapes window button on the left.

6. From the Chen's Database Notation stencil, drag an entity shape onto the drawing page.

7. Drag another entity shape onto the drawing page to create a second entity.

8. Drag a Relationship Connector onto the drawing page to create the relationship line.

9. To connect the entities, drag the left end of the relationship line to the first entity, and glue it to an attribute, a connection point, or the entire entity. Drag the other end of the relationship line, and glue it to the second entity.

10. Optionally, you may right-clicking the connector and select Show Multiplicity.

11. Drag a Relationship (to indicate a mandatory relationship) or an Identifying Relationship (for an optional relationship) and place it on top of the connector line. 

12. To add an attribute to an entity, drag one of the Attribute shapes from the Shapes pane to the entity. When the connecting line is over the entity, a green highlight line encloses the entity, indicating that the attribute will be glued to the entity when you release the mouse button. 

13. Optionally, you can right-click an attribute to make it required. A required attribute must have a value in it, while an optional attribute may not have a value in it and can be left blank.

Shapes available in Chen's database notation

Shape	What it represents
Entity	An object, a component of data. It can be uniquely identified by its attributes and therefore it's independent of any other entity in the schema. Also known as a "strong entity."
Weak Entity	An entity that can't be uniquely identified by its attributes alone. Its existence is dependent upon another entity (the "owner entity"). A weak entity’s identifier is a combination of the identifier of the owner entity and the partial key of the weak entity. The relationship between a weak entity and a strong entity is always denoted with an Identifying Relationship.
Associative Entity	An entity used in a many-to-many relationship. It represents an extra table in the database. All the relationships for this entity should be many.
Attribute	A fact that describes an entity.
Primary Key Attribute	An attribute that uniquely identifies a particular entity. The name of the attribute is underscored.
Multi-valued Attribute	An attribute that can have many values—that is, there are many distinct values entered for it in the same column of the table.
Derived Attribute	An attribute whose value is calculated, or derived, from other attributes. A derived attribute may or may not be physically stored in the database.
Relationship	Indicates the association between two strong entities. Its name is a verb that briefly describes the association.
Identifying Relationship	The relationship between a weak entity and a strong entity.
Relationship Connector	The line connecting two entities, indicating that they have an association. The relationship can be mandatory or optional. Once you've drawn a connector, you can change one or both ends to "optional" by right-clicking the connector and using the Set Begin Optional and Set End Optional commands.