title: How to group by using the prefix of a string i.e. the part before the first space?
body: <p>I have a table with a <code>varchar</code> column. The column contains sentences.<br>
  How can I group by sentences using their prefixes?<br>
  E.g. assume rows like this:  </p>
  
  <p>1| Word1 Word2 Word3<br>
  2| Word1 Word2 Word3    </p>
  
  <p>I want to group by the part of the string <em>before</em> the first space.<br>
  How can I do this?</p>