Consider which disciplines apply to your specific topic when choosing your databases.
Example: if you want to argue that the government should regulate the definition of "organic" food -- that's going to be a government subject as well as science (for agriculture). It's a current issue/event, too, so that's a third category to look under.
A database, generally speaking, is just a collection of info that: A) has been specifically selected to be included, and B) is designed for search and retrieval of the information.
More familiar databases, technically: Amazon (a database of stuff Amazon sells), Flickr (a photo database)
By contrast, Google is a search engine: a tool that tries to be aware of everything that's out there without any curation of that collection. Google doesn't pick and choose what sites it indexes, nor does it focus only on particular types or quality of sites. It's pretty indiscriminate.
Google Scholar is a specialized search engine of Google's that looks for scholarly material. It can be a little more flexible in search terms than the library databases, but it's harder to filter out articles you don't have access to.
Maybe you forget to limit your database search to available or full text content. Maybe you found something on Google Scholar that's behind a paywall. Maybe you want to locate a source that one of your existing sources cited and use it for yourself.
Alas, it cannot be found.
Usually not! Maybe you're absolutely desperate and you're down to 6 hours before the due date cutoff; in which case, sure.
But if you've got a couple days to spare, you can submit an inter-library loan request online. That department finds another library in the country that does have that article and can share with us, and then you will get a download link emailed to you. (Those links do expire, so...all the more reason to stay on top of your student inbox!).