I've restored a database and created a new user(same user from which I've logged in) as db_owner. Now when I wanted to see database diagram got an error
Database Diagram support objects cannot be installed because this database does not have a valid owner. To continue, first use files page of Database Properties dialog box or the Alter Authorization statement to set the database owner to a valid login, then add the database support objects
Now when I tried to change ownership from Files page of Database Properties I am getting error as
Set Owner failed for Database 'ABC' . (Microsoft.SqlServer.SMO) Additional Info: an exception occurred in SMO The proposed new database owner James-PC\James is mapped as user James in this database. Parameter name: James-PC\James"
Please help me fix the issue so that I may be able to see database diagrams on this computer after restoring the database backup from another system.