title: RODBC sqlSave not all columns
body: <p>How can I make sqlSave to write only a subset of columns.</p>
  
  <p>I've a (MS-Access) table with e.g. columns A, B, C en D and if I send a sqlSave command with a data frame with columns A, B and D (no C) I get the message:</p>
  
  <pre><code>Error in odbcUpdate(channel, query, mydata, coldata[m, ], test = test,  :
    missing columns in 'data'
  Calls: sqlSave -&gt; sqlwrite -&gt; odbcUpdate
  </code></pre>
  
  <p>(The columns in my table are all defined optional)</p>
  
  <p>I can add a dummy column to my data frame with name C and value NA and sqlSave will be happy, but is there another way to do this? Are there arguments of <code>sqlSave</code> I can use? I can't find them in the documentation.</p>