Relationships in the Logical Model › Relationship Cardinality

Relationship Cardinality

You can set the cardinality for the relationships in your model. Relationship cardinality represents the fact that each parent entity or table within a relationship is connected to a particular number of instances of the child entity or table. In IDEF1X, IE, and DM notations, the cardinality of a relationship can be represented in one of the following ways:

• Zero, one, or more - Signified by a blank space. Each parent in the relationship is connected to zero, one, or more instances of the child entity or table.
• One or more - Signified by the letter P. Each parent in the relationship is connected to one or more instances of the child entity or table.
• Zero or one - Signified by the letter Z. Each parent in the relationship is connected to zero or one instance of the child entity or table.
• Exactly - Each parent in the relationship is connected to an exact number of instances of the child entity or table. You specify the number of instances.

You can optionally display the cardinality symbols for a relationship at the child end of a relationship line.

When you create a non-identifying relationship you can choose whether a parent is required for each child by setting the null option for the relationship.

More information:

Relationship Null Options