Can I upload a single before my album, and then include that single on my album?

Yep!

Just upload the single first, and then upload the entire album (including the single) as a separate release. Once the full release is in stores, you can choose to leave the single, or remove it and only have the album version available.

Note: Use your existing ISRCs, the exact same audio file as in your original upload, same metadata (track titles, artist name, etc.) this might help retain play counts/playlists for the single in some stores. Nothing that we (or stores) can guarantee, however.

Related: