MYSQL Distinct results from a query - mysql

Question

What i'm trying to do is get the DISTINCT results using a MYSQL query:
$sql = "SELECT un.*, co.order_product_quantity AS product_num, cu.first_name, cu.surname, cp.product_name, cp.product_thumbnail AS prod_img, co.order_goods_cost, co.order_delivery_cost, co.order_status as status
FROM (
SELECT DISTINCT order_unique_id AS o_id, order_date
FROM cbs_orders
GROUP BY order_unique_id
) un
INNER JOIN cbs_orders co ON co.order_unique_id = un.o_id
INNER JOIN cbs_users cu ON cu.id = co.order_user_id
INNER JOIN cbs_products cp ON cp.product_id = co.order_product_id
ORDER BY un.order_date DESC LIMIT $start_from, $num_rec_per_page ";
I'm looking to get the DISTINCT order_unique_id from the query, i never wrote the query initially, i thought adding "SELECT DISTINCT order_unique_id" would solve the issue but it still brings back duplicate ids.
cheers for any help guys
Graham

Answer 1

You want to leverage GROUP BY correctly; DISTINCT won't help you in this situation. Additional, I'm pretty sure that sub-select is not needed.
Try this
$sql = "SELECT un.order_unique_id AS o_id, un.order_date,
co.order_product_quantity AS product_num,
cu.first_name, cu.surname, cp.product_name,
cp.product_thumbnail AS prod_img, co.order_goods_cost,
co.order_delivery_cost, co.order_status as status
FROM cbs_orders AS un
INNER JOIN cbs_orders co ON co.order_unique_id = un.o_id
INNER JOIN cbs_users cu ON cu.id = co.order_user_id
INNER JOIN cbs_products cp ON cp.product_id = co.order_product_id
GROUP BY un.order_unique_id
ORDER BY un.order_date DESC
LIMIT $start_from, $num_rec_per_page ";
This might produce odd results, because you are not applying aggregate functions to other columns. You may need to use those to get desired results.

Answer 2

Let me hazard a guess that you want records for only the most recent order. If this is the case, then you can do what you want, by properly aggregating the data:
SELECT un.*, co.order_product_quantity AS product_num, cu.first_name,
cu.surname, cp.product_name, cp.product_thumbnail AS prod_img,
co.order_goods_cost, co.order_delivery_cost, co.order_status as status
FROM (SELECT order_unique_id AS o_id, max(order_date) as order_date
FROM cbs_orders
GROUP BY order_unique_id
) un INNER JOIN
cbs_orders co
ON co.order_unique_id = un.o_id INNER JOIN
cbs_users cu
ON cu.id = co.order_user_id INNER JOIN
cbs_products cp
ON cp.product_id = co.order_product_id
ORDER BY un.order_date DESC
LIMIT $start_from, $num_rec_per_page;
If you want only one row per order, then you need to figure out what to do with the products. In my opinion, this interpretation is so different from your current question that you should ask another question, providing sample data and desired results.