查找值，其中從表2的值是行之間在表1

Question

假設以下結構：

項目：

ItemId Price 
---------------- 
1000 129.95 
2000 49.95 
3000 159.95 
4000 12.95 

閾值：

PriceThreshold Reserve 
------------------------ 
19.95   10 
100    5 
150    1 

-- PriceThreshold is the minimum price for that threshold/level 

我使用SQL Server 2008根據「PriceThreshold」中的項目價格落在何處返回「Reserve」。

實施例：

ItemId Reserve 
1000 5 
2000 10 
3000 1 

- 價格爲項目Id 4000是不低於最低的價格門檻所以應當從結果中排除更大。

理想情況下，我想只能使用一些直接的T-SQL，但如果我需要創建一個存儲過程來創建一個臨時表來存儲值，那很好。

Link to SQL Fiddle for schema

這晚，我想我的大腦關閉，所以任何幫助表示讚賞。

謝謝。

Answer 1

感興趣的東西是這樣的：

select 
    ItemId, 
    (select top 1 Reserve 
    from Threshold 
    where Threshold.PriceThreshold < Items.Price 
    order by PriceThreshold desc) as Reserve 
from 
    Items 
where 
    Price > (select min(PriceThreshold) from Threshold) 

SQLFiddle

Answer 2

一種方式去了解這是使用reserve爲範圍的下邊界，並使用lead解析功能，生成「下一個「下邊界，即上邊界。

一旦你完成了這一切，只需要考慮價格應該在兩個邊界之間的條件。不幸的是，between操作不處理null S，所以你需要使用一個有點沉重的條件來處理第一行和最後一行：

SELECT [ItemId], [Reserve] 
FROM Items 
JOIN (SELECT [PriceThreshold] AS [Bottom], 
       LEAD([PriceThreshold]) OVER (ORDER BY [PriceThreshold]) AS [Top], 
       [Reserve] 
     FROM [Threshold]) t ON 
       [Price] Between [Bottom] AND [Top] OR 
       ([Top] IS NULL AND [Price] > [Bottom]) OR 
       ([Bottom] IS NULL AND [Price] < [Top]) 

SQLFiddle solution

Answer 3

可以拿到較低以及綁定

select i.itemid, max(lo.pricethreshold) as lo 
from items i 
join threshold lo on lo.pricethreshold <= i.price 
group by i.itemid 

，並使用這個檢索儲備

with bounds as (select i.itemid, max(lo.pricethreshold) as lo 
       from items i 
       join threshold lo on lo.pricethreshold <= i.price 
       group by i.itemid) 
select i.itemid, t.reserve 
from items i 
join bounds b on b.itemid = i.itemid 
join threshold t on t.pricethreshold = b.lo 

SQLFiddle