获取一组列 (make.model) 的另一列（日期）最大值的一列（价格）的值

Question

我在 MS SQL

中有一个数据库 table

Date      Make    Model    Price
4-Apr-17  Toyota  Avalon   34000
5-Apr-17  Merc    ML350    45000
6-Apr-17  BMW     5X       55000
7-Apr-17  Totoya  Camry    28000
8-Apr-17  Merc    ML350    46000
9-Apr-17  BMW     5X       54000
10-Apr-17 Totoya  Camry    25000
11-Apr-17 Merc    ML350    47000
12-Apr-17 Toyota  Avalon   36000
13-Apr-17 BMW     5X       53000
14-Apr-17 Toyota  Avalon   35500
15-Apr-17 BMW     5X       53500
16-Apr-17 Toyota  Avalon   35500
17-Apr-17 Merc    ML350    46500

我想获取每个型号的最新价格。因此我的输出应该是

Date      Make    Model    Price
10-Apr-17 Totoya  Camry    25000
15-Apr-17 BMW     5X       53500
16-Apr-17 Toyota  Avalon   35500
17-Apr-17 Merc    ML350    46500

Answer 1

你应该使用 ROW_NUMBER:

WITH CTE AS
(
    SELECT *,
           RN = ROW_NUMBER() OVER(PARTITION BY Make, Model
                                  ORDER BY [Date] DESC)
    FROM dbo.YourTable
)
SELECT *
FROM CTE
WHERE RN = 1;

Answer 2

一种方法是使用 window 函数 row_number 和 top 1 with ties:

select top 1 with ties *
from your_table
order by row_number() over (
        partition by make, model 
        order by [date] desc
        );

这样可以避免subqueries/CTEs.

获取一组列 (make.model) 的另一列（日期）最大值的一列（价格）的值

Getting value of one column ( price ) for max of another column (date) for a set of columns (make.model)

sql-server

join

max

row-number