问题
I have a query which is something like this
SELECT
t.category,
tc.product,
tc.sub-product,
count(*) as sales
FROM tg t, ttc tc
WHERE t.value = tc.value
GROUP BY t.category, tc.product, tc.sub-product;
Now in my query I want to get top 10 products for every category (top by sales ) and for every category I need top 5 sub category (top by sales)
You can assume the problem statement as something like this :
Get top 10 products for each category by sales and for each product get top 5 sub-products by sales .
- Here category can be Books
- Product can be Harry Porter book
- sub productcan be HarryPorter series 5
Sample input data format
category |product |subproduct |Sales [count (*)]
abc test1 test11 120
abc test1 test11 100
abc test1 test11 10
abc test1 test11 10
abc test1 test11 10
abc test1 test11 10
abc test1 test12 10
abc test1 test13 8
abc test1 test14 6
abc test1 test15 5
abc test2 test21 80
abc test2 test22 60
abc test3 test31 50
abc test3 test32 40
abc test4 test41 30
abc test4 test42 20
abc test5 test51 10
abc test5 test52 5
abc test6 test61 5
|
|
|
bcd test2 test22 10
xyz test3 test31 5
xyz test3 test32 3
xyz test4 test41 2
Output would be "
top 5 rf for (abc) -> abc,test1(289) abc,test2 (140), abc test3 (90), abc test4(50) , abc test5 (15)
top 5 rfm for (abc,test1) -> test11(260),test12(10),test13(8),test14(6),test15(5) and so on
My query is failing because results are really huge . I am reading about oracle analytic functions like rank. Can someone help me modifying this query using analytical functions. Any other approach can also work.
I am referring to this http://www.orafaq.com/node/55. But unable to get a right sql query for this.
Any help would be appreciated..I am like stuck for 2 days on this :(
回答1:
There are probably reasons not to use analytical functions, but using analytical functions alone:
select am, rf, rfm, rownum_rf2, rownum_rfm
from
(
-- the 3nd level takes the subproduct ranks, and for each equally ranked
-- subproduct, it produces the product ranking
select am, rf, rfm, rownum_rfm,
row_number() over (partition by rownum_rfm order by rownum_rf) rownum_rf2
from
(
-- the 2nd level ranks (without ties) the products within
-- categories, and subproducts within products simultaneosly
select am, rf, rfm,
row_number() over (partition by am order by count_rf desc) rownum_rf,
row_number() over (partition by am, rf order by count_rfm desc) rownum_rfm
from
(
-- inner most query counts the records by subproduct
-- using regular group-by. at the same time, it uses
-- the analytical sum() over to get the counts by product
select tg.am, ttc.rf, ttc.rfm,
count(*) count_rfm,
sum(count(*)) over (partition by tg.am, ttc.rf) count_rf
from tg inner join ttc on tg.value = ttc.value
group by tg.am, ttc.rf, ttc.rfm
) X
) Y
-- at level 3, we drop all but the top 5 subproducts per product
where rownum_rfm <= 5 -- top 5 subproducts
) Z
-- the filter on the final query retains only the top 10 products
where rownum_rf2 <= 10 -- top 10 products
order by am, rownum_rf2, rownum_rfm;
I used rownum instead of rank so you don't ever get ties, or in other words, ties will be randomly decided. This also doesn't work if the data is not dense enough (less than 5 subproducts in any of the top 10 products - it may show subproducts from some other products instead). But if the data is dense (large established database), the query should work fine.
The below makes two passes of the data, but returns correct results in each case. Again, this is a rank-without-ties query.
select am, rf, rfm, count_rf, count_rfm, rownum_rf, rownum_rfm
from
(
-- next join the top 10 products to the data again to get
-- the subproduct counts
select tg.am, tg.rf, ttc.rfm, tg.count_rf, tg.rownum_rf, count(*) count_rfm,
ROW_NUMBER() over (partition by tg.am, tg.rf order by 1 desc) rownum_rfm
from (
-- first rank all the products
select tg.am, tg.value, ttc.rf, count(*) count_rf,
ROW_NUMBER() over (order by 1 desc) rownum_rf
from tg
inner join ttc on tg.value = ttc.value
group by tg.am, tg.value, ttc.rf
order by count_rf desc
) tg
inner join ttc on tg.value = ttc.value and tg.rf = ttc.rf
-- filter the inner query for the top 10 products only
where rownum_rf <= 10
group by tg.am, tg.rf, ttc.rfm, tg.count_rf, tg.rownum_rf
) X
-- filter where the subproduct rank is in top 5
where rownum_rfm <= 5
order by am, rownum_rf, rownum_rfm;
columns:
count_rf : count of sales by product
count_rfm : count of sales by subproduct
rownum_rf : product rank within category (rownumber - without ties)
rownum_rfm : subproduct rank within product (without ties)
回答2:
It's guesswork, but you could probably start from something like this:
drop table category_sales;
Some test data:
create table category_sales (
category varchar2(14),
product varchar2(14),
subproduct varchar2(14),
sales number
);
begin
for cate in 1 .. 10 loop
for prod in 1 .. 20 loop
for subp in 1 .. 30 loop
insert into category_sales values (
'Cat ' || cate,
'Prod ' || cate||prod,
'Subp ' || cate||prod||subp,
trunc(dbms_random.value(1,30 + cate - prod + subp))
);
end loop; end loop; end loop;
end;
/
The actual query:
select * from (
select
category,
product,
subproduct,
sales,
category_sales,
product_sales,
top_subproduct,
-- Finding best products within category:
dense_rank () over (
partition by category
order by product_sales desc
) top_product
from (
select
-- Finding the best Subproducts within
-- category and product:
dense_rank () over (
partition by category,
product
order by sales desc
) top_subproduct,
-- Finding the sum(sales) within a
-- category and prodcut
sum(sales) over (
partition by category,
product
) product_sales,
-- Finding the sum(sales) within
-- category
sum(sales) over (
partition by category
) category_sales,
category,
product,
subproduct,
sales
from
category_sales
)
)
where
-- Only best 10 Products
top_product <= 10 and
-- Only best 5 subproducts:
top_subproduct <= 5
-- "Best" categories first:
order by
category_sales desc,
top_product desc,
top_subproduct desc;
In that query, the column category_sales returns the sum of sales of the category in whose record it is returned. That means, every record of the same category has the same category_sales. This column is needed to order the result set with the best (sales) categories first (order by ... category_sales desc).
Similarly, product_sales is the sum of sales for a category-product combination. This column is used to find the best n (here:10) products in each category (where top_product <= 10).
The column top_product is "created" with the dense_rank() over... analytical function. For the best product in a category,it's 1, for the second best it's 2 and so on (hence the where top_product <= 10.
The columntop_suproduct is calculated in a similar fashion like top_product (that is with dense_rank).
来源：https://stackoverflow.com/questions/4966905/get-top-10-products-for-every-category