检查类别是否具有父级

i'm in mid of creating my own cms . And now i want to show which one of the category has parent but i don't know how, so please help me.

my category table

 idkategori  |  namakategori  | parentid 
      1         Programming         0
      2            PHP              1

Or i need relationship table for my categories?

My Controller so far.

function tampilmenu()
{
            $sql              = "select * from fc_kategori";
            $data['kategori'] = $this->bymodel->tampildata($sql);
            $sql1             = "select parentid from fc_kategori";
            $data['parent']   = $this->bymodel->tampildata($sql1);
                            $id=array();
                foreach ($data['parent'] as $paren)
            {
                $id[]=$paren->parentid;
            }
            foreach ($data['kategori'] as $cat) 
            if(in_array($cat->parentid,$id))
            {
                        $have ='Yes';
            }
            else
            {
                        $have ='No';
            }
            echo $cat->idkategori.$have;
                                    }   

}

my model

function tampildata ($sql)
{
    $query = $this->db->query($sql);
    return $query->result();
}

Please don't laugh on me.

Kindly follow:

1) Since you are using a MVC framework, never write queries inside the controller (queries should always be written in models).
2) Never use raw queries, since CI provides you what is called as Active Record.
3) Also never pass direct queries anywhere you'll possibly code in whichever language. Always pass data and make do that function to compute and query process.
4) Remember, in CI Models are only used for database functionalities, Views are only used for your HTML markups and Controllers acts as the mediator between models and views.

Your code:

Controller -

public function tampilmenu()
{
    $categories = $this->bymodel->get_category_having_parent();

    echo "<pre>"; print_r($categories);

    // this will return object having all categories that are parents
}

Model -

public function get_category_having_parent()
{
    $parent_ids = array();
    $ps = $this->get("parentid");
    foreach($ps as $p)
    {
       $parent_ids[] = $p->parentid;
    } 

    $this->db->where_in("id", $parent_ids);
    $query = $this->db->get("fc_kategori");
    return $query->result();
}

public function get($column="*")
{
    $this->db->select($column);
    $query = $this->db->get("fc_kategori");
    return $query->result();
}