What does a dashed / dotted relationship line repr

问题:

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?

回答1:

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

回答2:

referential integrity is not enforced