Codeigniter concat_ws not working - codeigniter

Question

Getting error when I tried like this:
$ci =& get_instance();
$ci->db->select("CONCAT_WS(' ',users.name_first,users.name_last) AS user_name,CONCAT_WS(' ',advertisers.name_first,advertisers.name_last) AS advertiser_name,image,advertiser_reviews.last_updated");
$ci->db->join('users', 'users.id = advertiser_reviews.user_id');
$ci->db->join('advertisers', 'advertisers.id = advertiser_reviews.advertiser_id');
$ci->db->order_by('advertiser_reviews.id','desc');
$ci->db->limit(1);
$query = $ci->db->get('advertiser_reviews');
Error as follows:
Error Number: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM (`hc_advertiser_reviews`) JOIN `hc_users` ON `hc_users`.`id` = `hc_advertis' at line 2
SELECT CONCAT_WS(' ', `hc_users`.`name_first`, `hc_users`.`name_last)` AS user_name,
CONCAT_WS(' ', `hc_advertisers`.`name_first`, `hc_advertisers`.`name_last)` AS advertiser_name,
`image`,
`hc_advertiser_reviews`.`last_updated`
FROM (`hc_advertiser_reviews`)
JOIN `hc_users` ON `hc_users`.`id` = `hc_advertiser_reviews`.`user_id`
JOIN `hc_advertisers` ON `hc_advertisers`.`id` = `hc_advertiser_reviews`.`advertiser_id`
ORDER BY `hc_advertiser_reviews`.`id` desc LIMIT 1

Answer 1

try to use $this->db->query("your sql query")
EDIT:
try to avoid the auto-quoting feature of the CodeIgniter DB class with
$this->db->select("your-query",FALSE)

Answer 2

There is sign ` at the Codeigniter generated code at the end
SELECT CONCAT_WS(' ', `hc_users`.`name_first`, `hc_users`.`name_last)`

Answer 3

$this->db->select('what of sql uncion' ,false);
the false tell ci to ignor escaping with `

Answer 4

Just came across this post where I had the same issue and you can get around the issue by a clever use of spaces.
$ci->db->select("CONCAT_WS(' ',users.name_first,users.name_last ) AS user_name )
As opposed to
$ci->db->select("CONCAT_WS(' ',users.name_first,users.name_last) AS user_name )
If you insert a space before the last closing bracket of the CONCAT_WS function then the CodeIgniter auto-quoting feature won't get confused about where the `s need to go. It also means you dont have to use the db->query() function.