SQL select動態記錄數

Question

這是一個非常奇怪的問題來描述，所以請裸露在我身邊。

使用SQL Server 2005，我試圖從一個表中選擇一定數量的記錄（動態），基於另一個表來獲取該記錄數量。

表1有一個類別ID和我想要爲該類別返回的記錄數。

Category ID TOP_Limit 
---------------------- 
Cat 1  1 
Cat 2  2 
Cat 3  10 

表2的產品ID，類別ID和產品數量：

Product ID Category ID Quantity 
--------------------------------- 
Part 1  Cat 1  10 
Part 2  Cat 1  20 
Part 3  Cat 2  100 
Part 4  Cat 2  100 
Part 5  Cat 2  50 
Part 6  Cat 3  5 

我如何編寫一個查詢，將讓我正確的「頂級」產品從表2的記錄（第2部分，第3部分& 4，第6部分）？

Answer 1

嘗試這樣：

;with cte as (
    select ProductID, CategoryID, Quantity, 
     [row] = row_number() over(partition by CategoryID order by Quantity desc) 
    from Table2 
) 
select t2.Product, t2.CategoryID, t2.Quantity 
from cte t2 
    join Table1 t1 on t2.CategoryID=t1.CategoryID 
where t2.row <= t1.TOP_Limit 

Answer 2

我認爲這樣做。

declare @Table1 table (
    Cat int, 
    TOP_Limit int 
) 

declare @Table2 table (
    Part int, 
    Cat int, 
    Quantity int 
) 

insert into @Table1 
    (Cat, TOP_Limit) 
    select 1,1 union all 
    select 2,2 union all 
    select 3,10 

insert into @Table2 
    (Part, Cat, Quantity) 
    select 2,1,20 union all 
    select 3,2,100 union all 
    select 4,2,100 union all 
    select 5,2,50 union all 
    select 6,3,5 

;with cteRowNums as (
    select t2.Part, t2.Cat, t2.Quantity, 
      ROW_NUMBER() over(partition by t2.Cat order by t2.Quantity desc, t2.Part) as rownum 
     from @Table2 t2 
      inner join @Table1 t1 
       on t2.Cat = t1.Cat 
) 
select c.Part, c.Cat, c.Quantity 
    from cteRowNums c   
     inner join @Table1 t1 
      on c.Cat = t1.Cat 
       and c.rownum <= t1.TOP_Limit