For some reason, I always forget to set permissions on the database in SQL Server when I am doing a database attach upgrade in SharePoint 2010.  I figure if I forget it a lot maybe other people do, so I thought I would post a quick tip on it.  Before even trying Test-SPContentDatabase or Mount-SPContentDatabase, make sure you open SQL Server and set the right permissions.  You need to edit the permissions on the account that you are running the PowerShell commands with and make this account a db_owner on the content database.  If you don’t, you will get an error stating that you don’t have the required permissions and you will look silly in front of your client.  :-)  It’s not a big deal to resolve, but I figure if I write this maybe I won’t forget to set it next time I do an upgrade.