查询错误，但我不知道它在哪里

Question

I am already look closely and see I miss something or not. But idk, still error, I'm already make insert sort of from, depending relationship. but still wrong, here, my code

$whls = querywheels("SELECT 
        c.pn_car, pc.pn_partcar, pc.name_partcar, p.name_proses,
        p.name_proses, p.name_proses, tc.cost_total, sp.total_price,
        r.rate_year, sp.total_all FROM secondproses AS sp 

          JOIN proses    AS p  ON sp.proses_1     = p.id_proses
          JOIN proses    AS p  ON sp.proses_2     = p.id_proses
          JOIN proses    AS p  ON sp.proses_3     = p.id_proses
          JOIN toolscost AS tc ON sp.cost_idfk    = tc.cost_id
          JOIN partcar   AS pc ON tc.partcar_idfk = pc.id_partcar
          JOIN car       AS c  ON pc.id_carfk     = c.id_car
          JOIN year_rate AS r  ON tc.rate_idfk    = r.rate_id
        ");

and this is my tables

this is my error

Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result,
boolean given in C:\xampp\htdocs\hwbase\PHP\connect.php on line 17

this is my function

function querywheels($sql)
    {
        global $con;
        //query ambil data

    $result = mysqli_query($con,$sql);
    /*$whls = mysqli_fetch_assoc($result);*/
    $rows = [];
        while ($whs = mysqli_fetch_assoc($result)) //this is line 17 
       {
            $rows []= $whs;
            # code...
        }
        return $rows;
    }

EDIT : the error is I'm using 3 alias in different join. Even if in same table (thanks to Benjamin Caure, tell me where is my fault)

Answer 1

At least I can see this error: you cannot use same alias "p" on different joins, even if it's the same table

    JOIN proses AS p1 ON sp.proses_1 = p1.id_proses
    JOIN proses AS p2 ON sp.proses_2 = p2.id_proses
    JOIN proses AS p3 ON sp.proses_3 = p3.id_proses