根据不同表中的ID计算所有行

Question

I want to count the photo based on product id . I think there is something to do in loop counting. So I coded as following but I got

Fatal error: Call to a member function fetch_assoc() on a non-object

<?
include_once($_SERVER['DOCUMENT_ROOT']."/cgi-bin/connect.php");

$stmt=$mysqli->prepare("select * from products_db order by prd_id");
$stmt->execute();
$result=$stmt->get_result();
$data=array();
while($row=$result->fetch_assoc()){
    //count no. of img in loop
    $stmt=$mysqli->prepare("select pic_id from photo_db where pic_sid=?");
    $stmt->bind_param('s',$row['prd_sid']);
    $result=$stmt->get_result();
    $nPic=$result->num_rows;

    $data[]=array($row['prd_code'],$row['prd_en'],$row['cat_id'],
number_format($row['prd_cost']),$row['prd_stts'],$nPic,$row['prd_rcm']);
}
echo json_encode(array('data' => $data));
?>

Then I do :

$stmt=$mysqli->prepare("select *,count(pic.pic_id) as npic 
from products_db prd 
inner join 
photo_db pic 
on prd.prd_sid=pic.pic_sid 
order by prd.prd_id");

It's working BUT SOME PRODUCTS WAS UNSHOWN BECAUSE NO RELATED pic_sid FROM photo_db

I want all product display the photo count even there's none of them existed in DB.

Answer 1

试试这个查询，我希望它能起作用。

select count(pi.pic_id),pr.* from photo_db pi where pi.pic_sid in (select pr.prd_sid from products_db pr ) group by pi.pic_id

Answer 2

Thank to the advice from @Sayed Mohd Ali . I come up with the solutions.

select *,
(select count(pic_id) as npic from photo_db where pic.pic_sid=prd.prd_sid) as npic
from products_db prd
left join photo_db pic on pic.pic_sid=prd.prd_sid
group by prd.prd_sid