如何使用窗口函数获取最高价格及其 id？答案

【问题标题】：How do I use window function to get max price and its id?如何使用窗口函数获取最高价格及其 id？
【发布时间】：2015-09-19 05:46:38
【问题描述】：

我有这个问题

select adate, factoryid, purchid, itemname, max(price) as price 
from tableb where catnum = 9
group by adate, factoryid, purchid, itemname
order by adate, factoryid, purchid, itemname

但我想要该行的 id。所以在一个完美的世界里：

select id, adate, factoryid, purchid, itemname, max(price) as price 
from tableb where catnum = 9
group by adate, factoryid, purchid, itemname
order by adate, factoryid, purchid, itemname

但我知道那行不通。

所以我尝试了这个：

select id, adate, factoryid, purchid, itemname, 
       max(price) over(partition by adate, factoryid, purchid, itemname) as price 
from tableb where catnum = 9

这行不通。所有 id 的价格都是重复的。查询结果集从 4000 行增加到 11000 行。

很明显，我弄错了窗口函数。首先，我做错了什么，其次，当然，我该如何解决？

【问题讨论】：

id 不是唯一确定的。你想要所有的 id 还是任何一个？

标签： sql tsql sql-server-2012 aggregate-functions window-functions

【解决方案1】：

SELECT  *
FROM    (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY adate, factoryid, purchid, itemname ORDER BY price DESC, id DESC) rn
        FROM    tableb 
        WHERE   catnum = 9
        ) q
WHERE   rn = 1

【讨论】：

【解决方案2】：

您可以使用 MAX 和 FIRST_VALUE 的窗口版本，可从 SQL Server 2012+ 获得：

SELECT DISTINCT adate, factoryid, purchid, itemname, 
       MAX(price) OVER (PARTITION BY adate, factoryid, purchid, itemname) AS price,
       FIRST_VALUE(id) OVER (PARTITION BY adate, factoryid, purchid, itemname
                             ORDER BY price DESC) AS id
FROM tableb 
WHERE catnum = 9
ORDER BY adate, factoryid, purchid, itemname

【讨论】：

【解决方案3】：

我不清楚你为什么想要这个 id 但是...... 假设

您想要条件的所有 ID
id 是 tableb 的 PK

那么这可能会起作用：

SELECT tableb.* FROM tableb
INNER JOIN
(
select adate, factoryid, purchid, itemname, max(price) as price 
from tableb where catnum = 9
group by adate, factoryid, purchid, itemname
) AS grouped
ON  tableb.adate = grouped.adate AND
    tableb.factoryid = grouped.factoryid AND
    tableb.purchid = grouped.purchid AND
    tableb.itemname = grouped.itemname AND
    tableb.price = grouped.price
order by tableb.adate, tableb.factoryid, tableb.purchid, tableb.itemname

【讨论】：