How to find Profit for Category - mysql

Question

My project is about a jewelery store and i try to find the profit of each product-category.
Let me be more specific
I have 3 tables which gives me the info:
SALES(salesid,productid,quantity,price)
salesid productid Quantity Price
11001 13001 4 5
11002 13002 6 10
11003 13003 5 16
.
.
11012 13012 7 15
RETURN(salesid,productid,date,quantity,price)
salesid productid Quantity Price
11003 13003 1 16
11007 13007 3 12
11008 13008 3 8
PROCUREMENT(procurementid,productid,quantity,price)
procurementid productid Quantity Price
100001 13001 10 2
100002 13002 10 2
.
.
100012 13012 10 2
product_category(categoryid,category)
categoryid category
1 Gold
2 Silver
.
5 Platin
product(Productid,categoryid)
Productid categoryid
13001 1
13002 3
.
.
13010 5
The profit is given from this type:
Profit=Quantity*Price(Sell)-Quantity*Price(Return)-Quantity*Price(Procurement)
And now here is the problem.. I came up to this so far
SELECT categoryid,
category,
(coalesce(a.rev,0)- coalesce(b.ret,0),
coalesce(c.cost,0)) AS profit
FROM product category AS g
JOIN product AS h ON g.categoryid = h.categoryid
JOIN
(SELECT categoryid,
sum(quantity*price) AS rev
FROM sales AS a,
product AS b
WHERE a.productid = b.productid
GROUP BY categoryid) a
LEFT OUTER JOIN
(SELECT cartegoryid,
sum(quantity*price) AS ret
FROM RETURN AS a ,
product AS b
WHERE a.productid = b.productid
GROUP BY categoryid) b ON a.categoryid = b.categoryid
LEFT OUTER JOIN
(SELECT categoryid,
sum(quantity*price) AS cost
FROM procurement AS a,
product AS b
WHERE a.productid = b.productid
GROUP BY categoryid) c ON a.categoryid = c.categoryid ,
product AS d,
procurement AS e
WHERE MONTH(f.date) = MONTH(e.date)
AND YEAR(date) = 2013
[sorry for the align i am new to the site dont know how to copy paste code well(:D)]
wahtever when i do this it comes to a state like
categoryid category profit
1 Gold -100
2 Silver -100
.
5 Platin -100
dont know where is the problem...i made a lot of changes and switches but nothing came up...any suggestion would be so helpfull.Thank u in advane

Answer 1

Initially looks like your profit formula has an extra comma in it.
this
(coalesce(a.rev,0) - coalesce(b.ret,0),coalesce(c.cost,0)) as profit
should be this
coalesce(a.rev,0) - coalesce(b.ret,0) - coalesce(c.cost,0) AS profit
Few more issues with this query
Right before the where clause, after you join the cost subquery, you add product and procurement tables but don't join them. This will cause a cartesian join which will throw off your results.
In the where clause you don't specify which tables date field you want to use. AND YEAR(date) = 2013 should be e.date or f.date. That should have given you an error if you tried to run it.
WHERE MONTH(f.date) = MONTH(e.date) which table is f.date referring to? You didn't give an alias of f to any table.
You join in procurement and use its date field to filter results by month, but none of your revenue, returns, and cost subquery totals take dates into account. This will throw off your results.