title: Auto increment issue in SQlite3
body: <p>I have a table in Sqlite3 :</p>
  
  <pre><code>CREATE TABLE `shows` (
      `index` INTEGER PRIMARY KEY AUTOINCREMENT,
      `show`  TEXT,
      `createddate`   TEXT,
      `Batch` INTEGER
  );
  </code></pre>
  
  <p>I'm loading data into the table using code below :</p>
  
  <pre><code>df = pd.DataFrame(np.column_stack([shows,dates, batch]),columns=['show', 'createddate','batch'])
  
  df.to_sql('shows', conn,if_exists='append')
  </code></pre>
  
  <p>The first time I ran it with the table empty it works fine.</p>
  
  <p>But if I run it again I get an error :</p>
  
  <pre><code> UNIQUE constraint failed: shows.index
  </code></pre>
  
  <p>Any ideas how I can get the index to auto-increment for the second load?  </p>
  
  <p>Edit : Show, Dates, Batch are just lists of text data.  You'll notice I'm not passing in the index as don't think I need to with AUTOINCREMENT on the primary key.</p>