SQL 查询以根据交易日期加入数据以获得本月和上月的成本

Question

我有一个交易数据集，其中包含 product_id、cost_unit、日期等列。产品成本每个月都在变化。我想要一个 table 具有以下结构

Product | Cost_from_this_Month | Cost_from_Previous_month

每个月可以有多个产品行，但该特定月份的费用是相同的。也就是说，一个月的费用是固定的。如何构建查询以获得我想要的结果？

我知道如何获取最近的费用：

  SELECT * FROM (
  SELECT Product, Cost_Unit
                    , Date
                        , zrank = row_number() OVER ( PARTITION BY Product ORDER BY Date DESC)
                FROM    MY_Table
            ) a where a.zrank = 1

谁能帮帮我？

Answer 1

如果您使用 SQL Server 2012 或更高版本，条件聚合和 lag() 函数如何？

select year(date), month(date), max(cost_unit) as thismonthcost,
       lag(max(cost_unit)) over (order by year(date), month(date)) as lastmonthcost
from my_table
group by year(date), month(date)

Answer 2

如果您使用 SQL Server 2012 或更高版本，可以使用 LEAD 或 LAG：

DECLARE @Products TABLE (
    Product VARCHAR(100),
    Cost_Unit MONEY,
    [Date] DATETIME
)
INSERT @Products VALUES
    ('Widget', 10, '1/1/2014'),
    ('Widget', 12, '2/1/2014'),
    ('Widget', 15, '3/1/2014'),
    ('Widget', 17, '4/1/2014'),
    ('Gizmo', 20, '1/1/2014'),
    ('Gizmo', 25, '2/1/2014'),
    ('Gizmo', 26, '3/1/2014'),
    ('Gizmo', 27, '4/1/2014')

SELECT
    Product,
    [Date],
    Products.Cost_Unit AS [Cost_This_Month],
    LAG(Products.Cost_Unit) OVER (PARTITION BY Product ORDER BY [Date]) AS [Cost_Last_Month]
FROM @Products Products
ORDER BY Product, [Date] DESC

这里的输出产生：

Product         Date                    Cost_This_Month       Cost_Last_Month
--------------- ----------------------- --------------------- ---------------------
Gizmo           2014-04-01 00:00:00.000 27.00                 26.00
Gizmo           2014-03-01 00:00:00.000 26.00                 25.00
Gizmo           2014-02-01 00:00:00.000 25.00                 20.00
Gizmo           2014-01-01 00:00:00.000 20.00                 NULL
Widget          2014-04-01 00:00:00.000 17.00                 15.00
Widget          2014-03-01 00:00:00.000 15.00                 12.00
Widget          2014-02-01 00:00:00.000 12.00                 10.00
Widget          2014-01-01 00:00:00.000 10.00                 NULL

如果您没有使用 SQL 2012 或更高版本并且无法使用这些新功能，那么带有 ROW_NUMBER 的 CTE 也将为您提供以下功能：

;WITH CTE AS (
    SELECT
        Product,
        [Date],
        Cost_Unit,
        ROW_NUMBER() OVER (PARTITION BY Product ORDER BY [Date] DESC) AS RowNum
    FROM @Products
)
    SELECT
        CM.Product,
        CM.Product,
        CM.Cost_Unit AS [Cost_This_Month],
        LM.Cost_Unit AS [Cost_Last_Month]
    FROM CTE CM
        LEFT OUTER JOIN CTE LM
            ON CM.Product = LM.Product
                AND CM.RowNum = LM.RowNum - 1

UPDATE 更新以说明一个月内的多笔交易。这假设该月的最后一笔交易是您当月使用的费用（例如，如果 5 月 1 日为 10 美元，5 月 5 日为 11 美元，则 5 月的 Cost_Unit 为 11 美元）。

-- LAG Solution
SELECT
    Product,
    [Date],
    Products.Cost_Unit AS [Cost_This_Month],
    LAG(Products.Cost_Unit) OVER (
        PARTITION BY Product ORDER BY [Date]) AS [Cost_Last_Month]
FROM (
    SELECT *, ROW_NUMBER() OVER (
        PARTITION BY Product, YEAR([Date]), MONTH([Date])
        ORDER BY [Date] DESC) AS RowNum
    FROM @Products
    ) Products
WHERE RowNum = 1
ORDER BY Product, [Date] DESC

-- ROW_NUMBER() Solution
;WITH CTE AS (
    SELECT
        Product,
        [Date],
        Cost_Unit,
        ROW_NUMBER() OVER (PARTITION BY Product ORDER BY [Date] DESC) AS RowNum
    FROM (
        SELECT *, ROW_NUMBER() OVER (
            PARTITION BY Product, YEAR([Date]), MONTH([Date])
            ORDER BY [Date] DESC) AS RowNum
        FROM @Products
        ) Products
    WHERE Products.RowNum = 1
)
    SELECT
        CM.Product,
        CM.[Date],
        CM.Cost_Unit AS [Cost_This_Month],
        LM.Cost_Unit AS [Cost_Last_Month]
    FROM CTE CM
        LEFT OUTER JOIN CTE LM
            ON CM.Product = LM.Product
                AND CM.RowNum = LM.RowNum - 1

SQL 查询以根据交易日期加入数据以获得本月和上月的成本

SQL query to join data based on transaction date to get this month's & previous month's cost

sql

tsql

sql-server