Question

Using SQL Server 2005, I am trying to select a certain number of records (dynamic) from one table, based on another table to get what that number of records needs to be.

Table 1 has a Category ID and the number of records I want returned for that category.

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

Table 2 has a Product ID, the Category ID, and a Quantity:

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  

How can I write a query that will get me the correct “top” product records from Table 2 (Part 2, Part 3 & 4, Part 6)?

Answer 1

Try something like this:

;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