title: Writing datetime.datetime() column using pandas.to_sql()
body: <p>I have a single column dataframe <code>df</code> which has column <code>TS</code> where</p>
  
  <pre class="lang-python prettyprint-override"><code>In [1]: type(df.TS.values[0])
  Out[1]: pandas.tslib.Timestamp
  </code></pre>
  
  <p>I convert the column to type <code>datetime.datetime()</code> </p>
  
  <pre class="lang-python prettyprint-override"><code>In [2]: import datetime
  In [3]: df['TS'] = df['TS'].astype(datetime.datetime)
  </code></pre>
  
  <p>I want to write this dataframe to a table in a mssql 2008 database using <code>pd.to_sql()</code>. So, I run the following.</p>
  
  <pre class="lang-python prettyprint-override"><code>In [4]: coltype = {'TS': sqlalchemy.TIMESTAMP}
  
  In [5]: df.to_sql(name='Table', con=engine, if_exists='append', index=False, dtype=coltype)
  Out[5]: ValueError: df (&lt;class 'sqlalchemy.sql.sqltypes.TIMESTAMP'&gt;) not a string
  </code></pre>
  
  <p>I have also tried not converting the column to <code>datetime.datetime()</code> and get same error. I have looked through the <code>sqlalchemy</code> documentation on column types but cannot figure out what parameter is supposed to pass. Can someone help me understand what I should be passing to write the column to the db as a datetime object?</p>