How to write mysql select query ( different from normal selection )

[eluser]suba[/eluser]
Hi all,

How to use CONCAT_WS(), DATE_FORMAT() function in select statement.

My sample 1.
------------

Code:

$this->db->select("DATE_FORMAT('field,'%d-%b-%Y')");
$this->db->get("tablename");

My sample 2.
------------

Code:

$this->db->select("CONCAT_WS('','field1','field2') as name ");
$this->db->get("tablename");

I wrote like this. but I have got error message.
How to write mysql function in select statement?