获取每个类别的前 10 名产品

Question

我有一个类似这样的查询

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;

现在，在我的查询中，我想要获取每个类别的前 10 个产品（按销售额排名最高），并且对于每个类别，我需要前 5 个子类别（按销售额排名最高）

您可以将问题陈述假设为如下所示：

获取每个类别（按销售额）排名前 10 的产品，并针对每个产品获取按销售额排名前 5 名的子产品。

• 这里的类别可以是书籍
• 产品可以是哈利·波特的书
• 子产品可以是哈利波特系列5

输入数据格式示例

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

输出将是“

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

我的查询失败了，因为结果非常巨大。我正在阅读有关 Oracle 分析函数（例如排名）的内容。有人可以帮我使用分析函数修改这个查询吗？任何其他方法也可以起作用。

我指的是这个http://www.orafaq.com/node/55。但无法为此获得正确的 sql 查询。

任何帮助将不胜感激..我在这件事上被困了两天:(

Answer 1

不使用分析函数而单独使用分析函数可能有以下原因：

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;

我使用 rownum 而不是排名，这样你就不会得到平局，或者换句话说，平局将是随机决定的。如果数据不够密集（前 10 个产品中的任何一个产品中的子产品少于 5 个 - 它可能会显示其他产品的子产品），这也不起作用。但如果数据密集（大型数据库），查询应该可以正常工作。

下面对数据进行了两次传递，但在每种情况下都返回正确的结果。同样，这是一个无排名查询。

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;

列：

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)