Ajax not calling on php query when joining multiple table - php

Question

I'm calling AJAX through below code on single table query and everything works fine and the results are printed:
public function getUnitsHTML() {
$jinput = JFactory::getApplication()->input;
$db = JFactory::getDbo();
$query = $db->getQuery(true);
$sdate = date_create($jinput->get ('dsvalue'));
$mystartdate = date_format($sdate, "Y-m-d");
$edate = date_create($jinput->get ('devalue'));
$myenddate = date_format($edate, "Y-m-d");
$query->select($db->quoteName(array('id', 'unit', 'start_date', 'end_date', 'state')));
$query->from($db->quoteName('#__p_reservations'));
$query->where($db->quoteName('state')." = ".$db->quote('1'),'AND')
->where($db->quoteName('start_date')." >= ".$db->quote($mystartdate),'AND')
->where($db->quoteName('end_date')." <= ".$db->quote($myenddate));
$query->order('ordering ASC');
$db->setQuery($query);
$results = $db->loadObjectList();
foreach ($results as $result)
{
echo '<option value="' . $result->id . '" > ' . $result->unit.'</option>';
}
exit;
}
But when trying to make it more complex by joining with other tables I'm getting 500 Error:
public function getUnitsHTML() {
$jinput = JFactory::getApplication()->input;
$db = JFactory::getDbo();
$query = $db->getQuery(true);
$sdate = date_create($jinput->get ('dsvalue'));
$mystartdate = date_format($sdate, "Y-m-d");
$edate = date_create($jinput->get ('devalue'));
$myenddate = date_format($edate, "Y-m-d");
$query
->select(array('a.unit','a.start_date','a.end_date','a.state','b.id','b.unit_number'))
->from($db->quoteName('#__p_reservations','a'))
->join('INNER',$db->quoteName('#__p_units','b') . ' ON (' . $db->quoteName('a.unit') . ' = ' . $db->quoteName('b.id') . ')')
->where($db->quoteName('a.state')." = ".$db->quote('1'),'AND')
->where($db->quoteName('a.start_date')." >= ".$db->quote($mystartdate),'AND')
->where($db->quoteName('a.end_date')." <= ".$db->quote($myenddate))
->order('ordering ASC');
$db->setQuery($query);
$results = $db->loadObjectList();
foreach ($results as $result)
{
echo '<option value="' . $result->id . '" > ' . $result->unit_number.'</option>';
}
exit;
}

Answer 1

your error is connected to mysql. It looks like your sql query is correct, but check back through the MYSQL command line. If the error goes on, this may be due to joomla JDbase.
I had an error with entering data in the database, but it had nothing to do with my code but with JDbase.
To make sure that the error is from joomla, put the joomla error console to work. It will tell you which file and line the error encounters.
Sorry for my bad English but it's not my mother tongue.

Answer 2

i did mistake on method of using order
->order('ordering ASC');
should change to:
->order($db->quoteName('a.unit'). 'ASC');