title: Show empty rows in a select SQLite query using pd.read_sql
body: <p>I want to create a pandas dataframe using a list of codes to search information in a SQLite table related to those codes. I know how to make the SQLite query giving a list of codes. The thing I want to add and I don't know how to do it is to add an empty row for those codes that we don't have information with the code and all the rest of the data empty, instead of ignoring that code as SQLite does. Here is an schematic example:</p>
  
  <pre><code>Code     atributes
  a        data
  b        data
  empty    -
  c        data
  c        data
  </code></pre>
  
  <p>where empty means a code that does not appear in the database.</p>
  
  <p>Thanks in advance!</p>