What does a dashed / dotted relationship line represent in SQL Management Studio - Database Diagram

Question

I'm looking at an existing database in Microsoft SQL Server Management Studio, and in the Database Diagram there is one relatioship that appears with a dashed or dotted line. The other relationships are all solid lines. What does the dashed line mean?

Solution 1

The dotted/dashed line means, that SQL Server does not enforce referential integrity for this relationship. Have a look here

Solution 2

referential integrity is not enforced