Sql server SQL Server:检测清单更改

我有一个简单的库存表：

IF OBJECT_ID('tempdb.dbo.#t') IS NOT NULL
    DROP TABLE #t
GO

CREATE TABLE #t
(
    [date] DATE,
    Item VARCHAR(1),
    [Location] INT,
    Qty INT
)

INSERT INTO #t ([date], [Item], [Location], [Qty]) 
VALUES ('2017-11-16', 'A', 1, 5),
       ('2017-11-16', 'B', 1, 5),
       ('2017-11-16', 'B', 2, 10),
       ('2017-11-16', 'A', 3, 1),
       ('2017-11-16', 'C', 3, 2),
       ('2017-11-16', 'A', 4, 20),
       ('2017-11-15', 'A', 1, 5),
       ('2017-11-15', 'B', 1, 5),
       ('2017-11-15', 'B', 2, 10),
       ('2017-11-15', 'A', 3, 1),
       ('2017-11-15', 'C', 3, 8),
       ('2017-11-14', 'A', 1, 10),
       ('2017-11-14', 'B', 1, 1),
       ('2017-11-14', 'B', 2, 10),
       ('2017-11-14', 'A', 3, 1),
       ('2017-11-14', 'C', 3, 8)

我想找出where子句中的日期，以及过去位置项目级别的数量差异

因此，结果应如下所示：

+------------+------+----------+-----+------------+---------+
|    Date    | Item | Location | Qty | LastChange | LastQty |
+------------+------+----------+-----+------------+---------+
| 16.11.2017 | A    |        1 |   5 | 14.11.2017 |      10 |
| 16.11.2017 | B    |        1 |   5 | 14.11.2017 |       1 |
| 16.11.2017 | B    |        2 |  10 |            |         |
| 16.11.2017 | A    |        3 |   1 |            |         |
| 16.11.2017 | C    |        3 |   2 | 15.11.2017 |       8 |
| 16.11.2017 | A    |        4 |  20 |            |         |
+------------+------+----------+-----+------------+---------+

由于库存表相当大，如果可能的话，我希望避免使用窗口函数

我已自行加入库存表。但是，我很难找到一个子句来消除不相关的数据集

SELECT
    a.[date],
    a.Item,
    a.Location,
    a.qty,
    b.[date] LastChange,
    b.qty LastQty
FROM 
    #t a
LEFT JOIN 
    #t b ON a.Item = b.Item 
         AND a.location = b.location  
         AND b.date < a.date
WHERE   
    a.date = '2017-11-16'

您需要额外的左联接以消除冗余记录：

SELECT a.[date], a.Item, a.Location, a.qty,
       b.[date] LastChange, b.qty LastQty
FROM t AS a
LEFT JOIN t AS b 
   ON a.Item = b.Item AND a.location = b.location AND b.date < a.date AND a.qty != b.qty
LEFT JOIN t AS c 
   ON c.Item = b.Item AND c.location = b.location AND c.date < b.date    
WHERE   
    a.[date] = '2017-11-16' AND c.Item IS NULL

就像说：给我那些没有其他记录的b记录，c记录，日期更早的记录

使用第一个值窗口函数：

;WITH CTE AS (
    SELECT [date], [Item], [Location], [Qty],
           FIRST_VALUE([date]) OVER (PARTITION BY [Item], [Location] 
                                     ORDER BY [date]) AS LastChange,
           FIRST_VALUE([Qty]) OVER (PARTITION BY [Item], [Location] 
                                    ORDER BY [date]) AS LastQty
    FROM t
)
SELECT [date], [Item], [Location], [Qty],
       IIF([Qty] != [LastQty], LastChange, NULL) AS LastChange,
       IIF([Qty] != [LastQty], LastQty, NULL) AS LastQty
FROM CTE
WHERE [date] = '2017-11-16' 

请尝试此查询

DECLARE @ReportDate date='20171116'

SELECT
  curData.[date],
  curData.Item,
  curData.Location,
  curData.Qty,
  lastData.[date] LastChange,
  lastData.Qty LastQty
FROM
  (
    SELECT *
    FROM #t
    WHERE [date]=@ReportDate
  ) curData
OUTER APPLY
  (
    SELECT TOP 1 *
    FROM #t lastData
    WHERE lastData.Item=curData.Item
      AND lastData.Location=curData.Location
      AND lastData.[date]<curData.[date]
      AND lastData.Qty<>curData.Qty
    ORDER BY lastData.[date] DESC
  ) lastData

---

窗口函数可以比使用子查询更有效。请查找pivot以执行此操作。您使用的是哪个版本的SQL Server？另外，窗口函数的引入是为了提高这种情况下的性能，那么为什么不使用窗口函数呢？如果这样做有积极的影响，那么我很乐意使用窗口函数。服务器版本为11.0.6598.0。谢谢：-@JeanDoux：你是说在MSSQL中使用pivot函数？这不是只在一个专栏上起作用吗？我改变了答案。在我的第一个版本中，我忘记使用条件lastData.QtycurData.QtyHi，到目前为止，我从未真正使用过apply这个概念。我可能想进一步探讨这个问题。谢谢大家!@rasenkantenstein-SQL是一种了不起的语言。祝你在这条路上成功！非常感谢。在这里学到了很多。窗口功能确实必须更快！谢谢。但是使用第一个值时有一个问题。没有检测到中间变化。在您的演示中，您可以在C文章中看到这一点。最后一个变化应该是15.11。不是14.11。@rasenkantenstein所以你想在这种情况下检测最新的记录？如果您有多个更改，如“2017-11-16”、“C”、“3、2”、“2017-11-16”、“C”、“3、8”、“2017-11-16”、“C”、“3、5”，该怎么办。上次变更的日期和变更金额。这是一个每天创建一次的快照表，主键是日期+位置+项目。只有一种状态是可能的。然而，窗口函数确实非常快。

;WITH CTE AS (
    SELECT [date], [Item], [Location], [Qty],
           FIRST_VALUE([date]) OVER (PARTITION BY [Item], [Location] 
                                     ORDER BY [date]) AS LastChange,
           FIRST_VALUE([Qty]) OVER (PARTITION BY [Item], [Location] 
                                    ORDER BY [date]) AS LastQty
    FROM t
)
SELECT [date], [Item], [Location], [Qty],
       IIF([Qty] != [LastQty], LastChange, NULL) AS LastChange,
       IIF([Qty] != [LastQty], LastQty, NULL) AS LastQty
FROM CTE
WHERE [date] = '2017-11-16' 

DECLARE @ReportDate date='20171116'

SELECT
  curData.[date],
  curData.Item,
  curData.Location,
  curData.Qty,
  lastData.[date] LastChange,
  lastData.Qty LastQty
FROM
  (
    SELECT *
    FROM #t
    WHERE [date]=@ReportDate
  ) curData
OUTER APPLY
  (
    SELECT TOP 1 *
    FROM #t lastData
    WHERE lastData.Item=curData.Item
      AND lastData.Location=curData.Location
      AND lastData.[date]<curData.[date]
      AND lastData.Qty<>curData.Qty
    ORDER BY lastData.[date] DESC
  ) lastData