Retrieve one saved variable from the database.

def get_var(self, key):
    'Retrieve one saved variable from the database.'
    vt = quote(self.__vars_table)
    data = self.execute(u'SELECT * FROM %s WHERE `key` = ?' % vt, [key], commit = False)
    if data == []:
      raise NameError(u'The DumpTruck variables table doesn\'t have a value for %s.' % key)
    else:
      tmp = quote(self.__vars_table_tmp)
      row = data[0]

      self.execute(u'DROP TABLE IF EXISTS %s' % tmp, commit = False)

      # This is vulnerable to injection
      self.execute(u'CREATE TEMPORARY TABLE %s (`value` %s)' % (tmp, row['type']), commit = False)

      # This is ugly
      self.execute(u'INSERT INTO %s (`value`) VALUES (?)' % tmp, [row['value']], commit = False)
      value = self.dump(tmp)[0]['value']
      self.execute(u'DROP TABLE %s' % tmp, commit = False)

      return value