Question

Possible Duplicate:
Get top 10 products for every category

I am looking for an Oracle query to get top 5000 stores and for each store get top 10 products and for each top 10 products get top 5 sub-products. So In total I should get 5000*10*5 rows.

Can someone help me get this using Oracle’s analytical functions.

My current query looks like

SELECT 
store,
product, 
sub-product,
 count(*) as sales 
 FROM stores_data
 GROUP BY store, product, sub-product;

Please assume table names as stores_data with columns store_id , product,sub_product

Answer 1

You should use dense_rank to get the top N rows.

Something like

SELECT
  storeid,
  store,
  productid,
  product,
  subproductid,
  subproduct
FROM
  (
    SELECT
      s.storeid,
      s.store,
      p.productid,
      p.product,
      sp.subproductid,
      sp.subproduct,
      dense_rank() over ( order by s.storeid) as storerank,
      dense_rank() over ( partition by s.storeid 
                          order by p.productid) as productrank
      dense_rank() over ( partition by s.storeid, p.productid 
                          order by sp.subproductid) as productrank
    FROM
      stores s
      INNER JOIN products p on p.storeid = s.storeid
      INNER JOIN subproduct sp on sp.productid = p.productid
  ) t
WHERE
  t.storerank <= 5000 and
  t.productrank < 10 and
  t.subproductrank < 5

Of course, I don’t now your tables nor the relation between them. And the actual fields and conditions you want to check for, so this is just a simple query getting the top N records based on their id. Also, this query expects a product to have only one store which might not be the case.. At least it will show you how to use dense_rank to get a three-layered sorting/filtering.