Database diagram support objects cannot be installed because this database does not have a valid owner.

after  I restore a database, I can't create the diagram.

error message:

Database diagram support objects cannot be installed because this database does not have a valid owner.  To continue, first use the Files page of the Database Properties dialog box or the ALTER AUTHORIZATION statement to set the database owner to a valid login, then add the database diagram support objects.

 

1. Right click your database , choose properties.

2. Go to the file page.

3. Add sa owner

4. Click 'OK'