title: nvl multiple columns
body: <p>I select from two subqueries s1 and s2. If the value for a column in s2 is null can I use nvl to retrieve a column in s1?</p>
  
  <pre><code>select
      s1.name_last
      nvl(s2.proj_mgr, s1.func_mgr)
  from
      (...) s1
      left outer join
      (...) s2
  on
      s1.empid = s2.owner_id
  ;
  </code></pre>