When I create new databases in SQL Server and try to make database diagrams, I always get the following error:
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.
The solution is to set the owner of the database to “sa” or the service account for SQL Server. You can do this by the “ALTER AUTHORIZATION” statement as mentioned in the error message, or through “Properties”->”Files” on the database.
The default owner when I create new databases is my login, and after some googling around, I found that it is a good idea to always use sa as the owner, and also that it’s not possible to change the default owner on new databases.