Question

我有一个包含item id，purchase date和item unit cost的购买明细表。

我想通过从每个商品ID中选择最新的前2条记录来获得平均商品购买成本。

Item id, purchase date, unitprice
1        3/1/2012        10
1        3/11/2012        8
2        3/1/2012        10
2        3/11/2012        10
1        2/1/2012        9
3        3/1/2012        10
3        3/11/2012        1
3        3/12/2012        13

我正在使用sql server 2008 r2

Answer 1

试试这个：

;WITH CTE AS (
    SELECT [Item id], [purchase date], unitprice, 
        ROW_NUMBER() OVER(PARTITION BY [Item id] ORDER BY [purchase date] DESC) rn
    FROM your_table
)
SELECT [Item id], [purchase date], unitprice
FROM CTE
WHERE rn < 3

我不确定如何使用最新的两条记录来计算平均值，但如果需要，请确保可以在查询中添加GROUP BY。

也许是这样的：

-- CTE here --
SELECT [Item id], AVG(unitprice)
FROM CTE
WHERE rn < 3
GROUP BY [Item id]

Answer 2

;WITH CTE AS (
    SELECT    [Item id]
            , [purchase date]
            , [unitprice]
            , [avg] = AVG([unitprice]) OVER(PARTITION BY [Item id])
            , [rnum] =  ROW_NUMBER() OVER(PARTITION BY [Item id] ORDER BY [purchase date] DESC)
    FROM    T
)
SELECT [Item id], [purchase date], [unitprice], [avg]
FROM CTE
WHERE rnum < 3

Answer 3

SELECT AVG(unitprice) as price from yourtablename 
 where unitprice IN 
 (
    SELECT TOP 3 (unitprice) from yourtablename
     where itemid='1'
     ORDER BY unitprice Desc
 );

通过下拉列表或文本框获取itemid。对你有用吗？

从同一个表中的每个类别中选择前n个记录

3 个答案: