unable to execute codeigniter query - php

Question

i am trying to execute query like: select*from bookdetails where quantity>0 ORDER BY created_date DESC
but i am getting error like Call to a member function num_rows() on a non-object in...
Please help me to solve this issue.
public function get_all_book_list_ByCreatedDateDSC($limit, $start,$sortsesval)
{
$this->load->database();
$this->db->limit($limit, $start);
$query=$this->db->join('coverdetails', 'coverdetails.cover_id = bookdetails.cover_id')->order_by('created_date', 'DESC')->get_where('bookdetails',array('quantity >', '0'));
if ($query->num_rows() > 0)
{
foreach ($query->result() as $row)
{
$data[] = $row;
}
return $data;
}
return false;
}

Answer 1

Try This:
$this->db->select('*');
$this->db->where('quantity >', $id);
$this->db->join('coverdetails', 'coverdetails.cover_id = bookdetails.cover_id');
$this->db->order_by('bookdetails.created_date', 'desc');
$this->db->limit($limit, $start);
$query = $this->db->get('bookdetails');
if($query -> num_rows() == 1)
return $query->result_array();
else
return false;

Answer 2

Your error message is telling you that $query is not an object. You cant call a member function on a non-object!
Your "join" method is not returning an object.
Try putting print_r($query) or var_dump($query) after you set $query, to find out exactly WHAT it is.

Answer 3

Try your function like this
public function get_all_book_list_ByCreatedDateDSC($limit, $start,$sortsesval)
{
$this->load->database();
return $this->db
->join('coverdetails', 'coverdetails.cover_id = bookdetails.cover_id')
->order_by('created_date', 'DESC')
->limit($limit, $start)
->get_where('bookdetails',array('quantity >', '0'))
->result_array();
}
When your query returns null(found no record) you wont be able to access the object because in $query it is null. You need to return the data in array format so use result_array. For detail see here; Using this you dont need to loop through object. It will give you ready-made array.
In the controller you can check if the result is null or array.