am i writing this update query correctly?

this is the sql query开发者_如何学JAVA i used before i switch to codeigniter

UPDATE transaction SET due_amount = to_pay-$payment_amount WHERE id = '$id'

with codeigniter

$this->db->set('due_amount', 'to_pay-'.$payment_amount, FALSE);                
$this->db->where('id', $id); 
$result = $this->db->update('transaction');

in the codeigniter code am i writing $this->db->set correctly?

Regards

You should do it like this:

$this->db->where('id', $id); 
$result = $this->db->update('transaction',array('due_amount'=>'to_pay-'.$payment_amount));

Hope this helps.

There are multiple variants to use the update^Docs function. Yours doesn't look specifically bad (I would however don't bypass escaping if not for a specific reason), maybe you prefer to use an array (or object) to provide the data being updated:

$data = array(
    'due_amount' => 'to_pay-'.$payment_amount,
);
$this->db->update('transaction', $data, sprintf('id = %d', $id));

I think here could be some issue with $this->db->set Standard way of updating content in codeignitor is this

$data = array(
           'title' => $title,
           'name' => $name,
           'date' => $date
        );

$this->db->where('id', $id);
$this->db->update('mytable', $data); 

Produces: UPDATE mytable SET title = '{$title}', name = '{$name}', date = '{$date}' WHERE id = $id