Question

So I have these 2 tables and I’m trying to write the most efficient query to output the distinct coupons for each manufacturer:

Manu Table
manu_id    manu_name
   1        Fujitsu 
   2           HP
   3        Brother

Products Table
prod_id    manu_id    prod_type   prod_coupon_img
    1         2          A4            1.jpg
    2         2         paper          1.jpg
    3         2         boxes          2.jpg
    4         3          ink           3.jpg

This query:

$sql = mysql_query("SELECT m.manu_id, p.prod_id, p.prod_type, p.prod_coupon_img
                    FROM manu m INNER JOIN products p 
                    WHERE m.manu_id=2 AND m.manu_id=p.manu_id");

Outputs:

prod_id    manu_id    prod_type  prod_coupon_img
    1         2          A4           1.jpg
    2         2         paper         1.jpg
    3         2         boxes         2.jpg

and this query:

$sqlDistinctCoupons = mysql_query("SELECT DISTINCT m.manu_id, p.prod_coupon_img 
                                   FROM manu m INNER JOIN products p 
                                   WHERE m.manu_id=2 AND m.manu_id=p.manu_id");

Outputs:

manu_id    prod_coupon_img
   2            1.jpg
   2            2.jpg

What I’m trying to accomplish now is to show the unique coupons HP is offering, so one for (A4 & paper), and one for boxes.
Here is my code to output that:

$DistinctCoupons .=   'Showing coupon for $row["prod_type"] products <img id="$row["prod_id"]" src="$row["prod_coupon_img"]" />';

How can I do this, how can I mix both queries to just one and output the distinct coupons? I tried 2 while loops but that didn’t work, and I’ve been reading that you shouldn’t use 2 while loops on db calls anyways, as it puts a lot of unneeded strain. Any ideas?

Answer 1

$manu_name = mysql_real_escape_string($_POST['manu_name']);
$query = "SELECT p2.prod_type, p2.prod_id, p2.prod_coupon_img
FROM products p2 
WHERE p2.id IN (
  SELECT Min(p.id)
  FROM products p 
  INNER JOIN manu m ON (m.manu_id = p.manu_id)
  WHERE m.manu_name = '$manu_name'
  GROUP BY prod_coupon_img) ";