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.
Usually this happens when you move a database to another server where the owner of the database is unknown. Best example is when attach AdventureWorks database and then try to open “Database Diagrams” folder.
USE [DatabaseName] -- Change the database name here GO ALTER AUTHORIZATION ON DATABASE::DatabaseName TO sa GO EXEC dbo.sp_changedbowner @loginame = N'sa', @map = false GO