query in codeigniter 3 code example

Example 1: codeigniter raw query

$sql="Select * from my_table where 1";    
    $query = $this->db->query($SQL);
    return $query->result_array();

Example 2: raw query in codeigniter

$query = $db->query('YOUR QUERY HERE');

Example 3: codeigniter select for update

$table = "my_table";
$id = 1;
$update = ["status"=>"working"];
//Edit just above /\ if you don't need extra "where" clause
$query = $this->db->select()
            ->from($table)
            ->where('id', $id)
            ->get_compiled_select();
$data = $this->db->query("$query FOR UPDATE")->row_array();
$this->db->where('id', $data['id'])->update($table,$update);