When you restore the database backed up from another machine to your machine and click the database relationship diagram of this database in SSMs, the following prompt is displayed:
The database does not have a valid owner, so you cannot install the database relational diagram support object. To continue, first set the database owner to a valid login name using the "file" page or the alter authorization statement in the "database properties" dialog box, and then add a database relational diagram support object.
The database is determined to have a database relationship diagram. The following two methods are provided: the first method is difficult to use after several attempts, and the second method is successful. Specifically, run the following command in SSMs:
Alter authorization on Database: mydbname to sa
Modify mydbname to the actual database name, and set the owner to sa.
For detailed parameters of alter authorization, refer to the following address:
Http://msdn2.microsoft.com/zh-cn/library/ms187359.aspx