title: How can I merge the columns from two tables into one output?
body: <p>I have two tables with similar information. Let's call them <code>items_a</code> and <code>items_b</code>. They should be one, but they are coming from different sources, so they aren't. When I full-join the two table, some rows end up with data from either one or both tables. One of the columns in both tables is <code>category_id</code>. I would like to cross the combined table with the categories table using <code>category_id</code>. However, I have two <code>category_id</code> columns now (one from <code>items_a</code> and one from <code>items_b</code>). Is there a way to merge the two columns into one?</p>
  
  <p>I hope this isn't too confusing of a question.</p>