SQL Server management studio allows you to have Database Diagrams to graphically show the structure of the database. In addition, you can create and modify tables, columns, relationships, and keys. Plus, you can modify indexes and constraints.
While trying to Create a New Database Diagram you might come across to the following error:[box type=”info” width=”100%” ]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.[/box]
To address this problem you might consider granting access to [sa] database account:
ALTER AUTHORIZATION ON DATABASE::DatabaseName TO [sa];
Or if you want to change the owner to that local Administrator account, then it should be:
ALTER AUTHORIZATION ON DATABASE::DatabaseName TO [PCName\Administrator];