title: Please explain these Python Fetch types
body: <p>What is the difference between these fetching.?
  please give me a examples for reference site to get clear idea.still i'm confuse with it</p>
  
  <pre><code>res = cr.dictfetchall()
  
  res2 = cr.dictfetchone()
  
  res3 = cr.fetchall()
  
  res4 = cr.fetchone()
  </code></pre>
  
  <p>cr is the current row, from the database cursor  (OPENERP 7 )</p>
  
  <p>ex : </p>
  
  <pre><code>def _max_reg_no(self, cr, uid, context=None):
      cr.execute("""
      select register_no as reg_no
      from bpl_worker
      where id in (select max(id) from bpl_worker)
      """)
      res = cr.fetchone()[0]
      print (res)
      return res
  </code></pre>