Complex query with many joins - mysql

Question

I am trying to make one query, to get some statistic data from database.
My tables structure described here:
PRODUCTS
id | price | buy_price | vendor_code | ...
ORDERS
id | shipping_method_id | ...
ORDER_ITEMS
id | order_id | product_id | quantity | ...
SHIPPING_METHODS
id | cost | ...
SUPPLIERS
id | code | ...
I want to get data like this. In words, I am making reports on Product total income, expenses and quantity of buys in my ecommerce, and want them to group by supplier. I wrote this sql:
SELECT orders.id,
suppliers.code,
COUNT(products.id)*items.quantity buys,
SUM(products.price*items.quantity + shipping_methods.cost) sales,
SUM(products.buy_price*items.quantity) expenses
FROM `orders` orders
INNER JOIN `order_items` items ON items.order_id = orders.id
INNER JOIN `products` products ON items.product_id = products.id
INNER JOIN (SELECT DISTINCT suppliers.code FROM `suppliers`) suppliers
ON products.vendor_code LIKE CONCAT(suppliers.code, '%%')
INNER JOIN `shipping_methods` shipping_methods ON orders.shipping_method_id = shipping_methods.id
WHERE (
orders.delivery_date_to BETWEEN '2011-11-18' AND '2011-11-19'
)
GROUP BY suppliers.code, orders.id
ORDER BY buys DESC
this returns to me this data:
order_id code buys sales expenses
85 SB 4 1504 1111.32
84 VD 2 496 350.82
60 lg 2 1418 1052.31
88 SB 1 376 277.83
When I change GROUP BY suppliers.code, orders.id to GROUP BY suppliers.code, it returns almost correct data, I mean data is grouped by code, but counting is wrong. Admit that sales and expenses are correct
order_id code buys sales expenses
85 SB 8 1880 1389.15
60 lg 2 1418 1052.31
84 VD 2 496 350.82
If u see SB counted total 8 sales, but really there are only 5, as u can see in previous table. I'm sure I missed something in my query, but cant understand how to correct this.
PS field order_id are unused in my further scripts, I use it because django's Model.objects.raw() query does need to have primary key in result, don't really understand why

Answer 1

try this query.
SELECT t1.code, SUM(t1.buys), SUM(t1.sales) FROM (
SELECT orders.id,
suppliers.code,
COUNT(products.id)*items.quantity buys,
SUM(products.price*items.quantity + shipping_methods.cost) sales,
SUM(products.buy_price*items.quantity) expenses
FROM `orders` orders
INNER JOIN `order_items` items ON items.order_id = orders.id
INNER JOIN `products` products ON items.product_id = products.id
INNER JOIN (SELECT DISTINCT suppliers.code FROM `suppliers`) suppliers
ON products.vendor_code LIKE CONCAT(suppliers.code, '%%')
INNER JOIN `shipping_methods` shipping_methods ON orders.shipping_method_id = shipping_methods.id
WHERE (
orders.delivery_date_to BETWEEN '2011-11-18' AND '2011-11-19'
)
GROUP BY suppliers.code, orders.id
ORDER BY buys DESC
) AS t1
GROUP BY t1.code
Edit: I've forgotten SUM() parts. Just added, please retry if you've already tried.