How do I test if my MySQL query was successful

if ($this->db->affected_rows() > 0)
{
  return TRUE;
}
else
{
  return FALSE;
}

or

if ($this->db->affected_rows() > 0)
  return TRUE;
else
  return FALSE;

or

return ($this->db->affected_rows() > 0) ? TRUE : FALSE;

also(much better)

return ($this->db->affected_rows() > 0);

A better solution I’ve found is to manage the difference between an ERROR and 0 affected rows. 0 affected rows is not necessarily a bad thing, but an error is something you do want to know about:

if ($this->db->_error_message()) {
    return FALSE; // Or do whatever you gotta do here to raise an error
} else {
    return $this->db->affected_rows();
}

Now your function can differentiate…

if ($result === FALSE) {
    $this->errors[] = 'ERROR: Did not update, some error occurred.';
} else if ($result == 0) {
    $this->oks[] = 'No error, but no rows were updated.';
} else {
    $this->oks[] = 'Updated the rows.';
}

Just some quick hacking there – you should obviously make the code far more verbose if you have other people using it.

The point is, consider using _error_message to differentiate between 0 updated rows and a real problem.