title: Access query to pull records that are max of one record but unique of another
body: <p>I tried adapting sql from <a href="https://stackoverflow.com/questions/17592737/access-query-to-select-rows-that-are-the-max-of-one-column-but-unique-on-another">here</a> I must be doing something wrong (I know I am because I'm lost when it comes to SQL)  Here's my sample table:  I want the max ID with unique Trailer </p>
  
  <pre><code>|--ID--|Trailer|--To--|Load Qty A|Load Type/Config A|
  |  1   | A100  |  B6  |     2    |        A1        |
  |  2   | A100  |  A4  |     1    |        A1        |  &lt;-Show this
  |  3   | B099  |  B2  |     6    |        C23       |  &lt;-Show this
  |  4   | A027  |  N10 |     3    |        O1        |
  |  5   | J400  |  A4  |     8    |        A1        |  &lt;-Show this
  |  6   | A027  |  A4  |     4    |        B24       |  &lt;-Show this
  </code></pre>
  
  <p>I understand this is basically the same structure as the post linked above, but I really cannot get it to work.  I thought that I had it working simply by having everything in the query as "last" except for trailer which I had "group by" but it started outputting incorrect records.</p>