As you're using custom SQL (I presume), you'll have to add these to the select statement.
Alex - Thanks for the reply.
I just figured out my problem. I was using SQL Server 2008 Management Studio for the 1st time yesterday (was an MS Access user prior) and I setup a view in SQL Server to handle the join and the selection of the appropriate fields, nowing I was going to add new fields to the tables behind the view in the near future. I just updated my view in SQL Server and refreshed my data connection and the fields are now in Tableau.
Sorry for wasting your time and thank you!