php - using aggregate function in codeigniter query -

i trying write below query in codeigniter format , getting problem aggregate function:

$stmt = "select sum(subscription_amt) samt, bill_month,                  sum(loan_refund_amt*no_of_loan_installment+error_amt) lamt           pf_bill_det           trim(pf_number)='$pfno'                 , fin_year='$fyear'                 , aproved='y' group bill_month"; $query = $this->db->query($stmt); 

this query ending error loan_refund_amt*no_of_loan_installment+error_amt not column. please me how write query using codeigniter query format.

why don't try this

$this->db->select("count(*) mycount"); $this->db->from("mytable"); $this->db->where("field", $value); $this->db->get(); 

or

$this->db->select("sum(field_name) mysum"); $this->db->from("mytable"); $this->db->where("field", $value); $this->db->get(); 

or

$this->db->select("sum(field_name) mysum, username, password"); $this->db->from("mytable"); $this->db->where("field", $value); $this->db->get(); 

but

in simple query function can use

$query = $this->db->query("select count(field_name) total_names, fname");

$query->result(); \\ returns array of objects

$query->result_array(); \\ returns result pure array

$query->row(); \\ returns single result , first row