title: column reference is ambiguous sql error
body: <p>I'm trying to join 4 different table to calculate item revenue depending on some conditions ,I will write sql query after I'm able to build the right view using 4 tables ...below is the query for the view and I'm getting ambiguous column error for ik...can someone please explain why?
  Thanks for your help!</p>
  
  <pre><code>select top 5 g.*
  from (
      select *
      from (
          (
              select a.ik
                  ,b.upc as upc
                  ,b.class
                  ,a.units
              from Tbl1 a
              join TBL2 b
                  on a.ik = b.ik
              ) c join Tbl3 d
              on c.ik = d.ik
          ) e
      join Tbl4 f
          on e.ik = f.ik
      ) g
  </code></pre>