title: concatenating columns at query level in sqlalchemy
body: <p>Is it possible to combine two columns when querying in sqlalchemy?</p>
  <p>For example, I have following table:</p>
  <pre><code>table 1                      table 2
  col1   col2   col3           col1   col2  col3
  A       123     1             ABC    A1B2
  B       456     2             DEF    C3D4
  C       789     3             GHI    E5F6
  </code></pre>
  <p>I would like my query to look something like this:</p>
  <pre><code> session.query(table.col3, (table1.col2 + table2.col2)).join(table2)
  </code></pre>
  <p>And would like the following results:</p>
  <pre><code>(1, 123A1B2)
  (2, 456C3D4)
  (3, 789E5F6)
  </code></pre>
  <p>How would I go about doing that?</p>