SQL Query (max of sum per year) - sql

Question

I will try to describe my problem here. Let's say that i have 3 tables:
1. sales
salesID (PK)
productID(FK) - FK that points to the sold product
storeID(FK) - FK that points to the store that sold the product
month - month in which the product was sold
year - year in which the product was sold
amount - amount(of money) for which the product was sold
2. product
productID (PK)
productName
3. store
storeID (PK)
storeName
I need the following query: For every store show the top selling product in that store for the specified year. So the result should look something like:
STORE PRODUCT AMOUNT
store1 product1 XXX amount
store2 product2 YYY amount
store3 product1 XYX amount
Where each amount would be the highest sum of all amounts in that year.
What I can do now is:
SELECT store.storeName
, product.ProductName
, SUM(sales.ammount)
FROM sales
JOIN product ON sales.productID = product.productID
JOIN store ON sales.storeID = store.storeID
GROUP BY store.storeName
, product.ProductName
WHERE sales.year = 'XXXX'
;
Where I get a sum per product and per store. After this I can use the cursor to go thru the entire table row by row and check which one has the highest amount for that store.
But I was wondering if it is possible to do that in a 'simple' query?
I'm using SQL Developer for Oracle 11g database.
And I would appreciate any help.

Answer 1

Not terribly familiar with Oracle, but perhaps something like:
WITH cte AS (SELECT store.storeName
, product.ProductName
, SUM(sales.ammount) as sales_amount
FROM sales
JOIN product ON sales.productID = product.productID
JOIN store ON sales.storeID = store.storeID
WHERE sales.year = 'XXXX'
GROUP BY store.storeName, product.ProductName
)
SELECT a.*
FROM cte a
JOIN (SELECT storeName
, MAX(sales_amount) as Max_Sales
FROM cte
GROUP BY storeName
)b
ON a.storeName = b.StoreName
AND a.sales_amount = b.Max_Sales;
If there's a tie that returns both entries, you can use ROW_NUMBER() instead to limit to one result per storeName .