We've got a Sitecore 7.5 installation where we did not deploy any xDB features. There's no Mongo DB or Analytics reporting DBs. We're now exploring upgrading to 8 and turning on these features. I'm doing a test upgrade on a dev server. I've got the Mongo DB set up, but there currently is no Analytics DB in SQL. How do I go about creating that DB?
When you download Sitecore 8 from https://dev.sitecore.net/ there is a zip of the webroot (e.g. from this page). Once you download that webroot zip, you can find the Sitecore.Analytics.mdf and Sitecore.Analytics.ldf files within the \Databases\ folder.