I am learning about the Crow's Foot notation, and there is something that I don't understand, some tutorials shows an Identifying Relationship as having a straight line, and a Non-Identifying Relationship as having a dashed line:
While other tutorials shows both relationships as having a straight line:
Are both notations correct?
The +O on the left side indicates it is non-identifying (optional) on the right side. This would be implemented as a nullable column on the right hand side. This is common to all tools I have worked with, and certainly the two tools you are working with.
The ends of the relationships have show two values (max and min) indicating the cardinality of the relationship for the table at the other end of the line. The min value has two possible cardinality values zero (O) or 1 (| or + ), The max value also has two possible diagrammed values 1 (| or +) or many (a crowsfoot). If either min value is zero, then the relationship is optional.
An identifying value must have a cardinality of (1-1). Some tools may show only one cardinality indicator for a (1-1) cardinality.
Some tools use dashed lines for optional relationships. Both notations are correct. I prefer the dashed lines format , especially when the diagram is large or busy. I have worked with tools that provide extensive capability to modify how the relationship lines are rendered such as modifying the linewidth, pattern and color.
