$this->db->get_where('table', array(
  'fld1' => 'val1',
  'fld2' => 'val2'
));

// result
select * from table where fld1 = 'val1' and fld2 = 'val2;


$this->db->where('fld2', 'val2');
$this->db->get_where('table', array(
  'fld1' => 'val1'
));

// result
select * from table where fld2 = 'val2' and fld1 = 'val1';


$this->db->start_cache();
$this->db->where('fld2', 'val2');
$this->db->stop_cache();

$this->db->get_where('table', array(
  'fld1' => 'val1'
));

$this->db->flush_cache();

// result
select * from table where fld2 = 'val2' and fld1 = 'val1';

$this->db->where('bo_table', 'test');
	
$this->db->start_cache();
$this->db->where('wr_id', '10');
$this->db->stop_cache();

$this->db->get_where('table', array(
  'is_comment' => 1
));

$this->db->flush_cache();

// result
select * from table where and wr_id = '10' bo_table = 'test' and is_comment = 1;