sql - 日期范围的最小值或最大值 - 根据产品 ID、价格和日期范围确定给定日期范围的最低价格

Question

我真的希望你们中的一些人喜欢挑战。我有一个产品 ID、价格和这些价格有效时的日期范围表。

+----+-------+---------------------+---------------------+
| Id | Price |      StartDate      |       EndDate       |
+----+-------+---------------------+---------------------+
|  1 |    19 | 2016-12-01 00:00:00 | 2017-12-01 23:59:59 |
|  1 |    18 | 2017-01-01 00:00:00 | 2018-01-12 23:59:59 |
|  1 |    17 | 2017-02-03 00:00:00 | 2017-03-03 23:59:59 |
|  1 |    16 | 2018-01-01 00:00:00 | 2018-03-02 23:59:59 |
|  2 |    15 | 2017-01-01 00:00:00 | 2017-03-05 23:59:59 |
|  2 |    15 | 2017-03-06 00:00:00 | 2017-03-31 23:59:59 |
|  2 |    30 | 2017-04-01 00:00:00 | 2017-05-03 23:59:59 |
|  3 |    12 | 2017-01-01 00:00:00 | 2017-01-31 23:59:59 |
|  3 |    12 | 2017-02-01 00:00:00 | 2017-02-28 23:59:59 |
|  4 |    14 | 2017-01-01 00:00:00 | 2017-04-05 23:59:59 |
|  4 |    14 | 2017-04-01 00:00:00 | 2017-04-30 23:59:59 |
|  4 |    12 | 2017-04-15 00:00:00 | 2017-05-30 23:59:59 |
|  5 |    20 | 2017-01-01 00:00:00 | 2017-01-31 23:59:59 |
|  5 |    20 | 2017-03-01 00:00:00 | 2017-03-31 23:59:59 |
|  6 |    15 | 2017-01-01 00:00:00 | 2017-01-31 23:59:59 |
|  6 |    15 | 2017-02-01 00:00:00 | 2017-02-28 23:59:59 |
|  6 |    15 | 2017-04-01 00:00:00 | 2017-04-30 23:59:59 |
+----+-------+---------------------+---------------------+

SQLFiddle: http://sqlfiddle.com/#!6/39288/1

我需要以一种格式获取它:

日期期间具有相同的 Id 和价格，“touch”(即 Id #3)合并为一个期间。

重叠的日期时间段(即 Id #4)合并为一个时间段。

显示每种产品的最低价格以及在什么范围内。

具有差距和相同价格的日期范围不会合并并且是单独的行(即 Id #5)。

结果应该是:

+----+-------+---------------------+---------------------+
| Id | Price |      StartDate      |       EndDate       |
+----+-------+---------------------+---------------------+
|  1 |    19 | 2016-12-01 00:00:00 | 2016-12-31 23:59:59 |
|  1 |    18 | 2017-01-01 00:00:00 | 2017-02-02 23:59:59 |
|  1 |    17 | 2017-02-03 00:00:00 | 2017-03-03 23:59:59 |
|  1 |    19 | 2017-03-04 00:00:00 | 2017-12-01 23:59:59 |
|  1 |    18 | 2017-12-02 00:00:00 | 2017-12-31 23:59:59 |
|  1 |    16 | 2018-01-01 00:00:00 | 2018-03-02 23:59:59 |
|  2 |    15 | 2017-01-01 00:00:00 | 2017-03-31 23:59:59 |
|  2 |    30 | 2017-04-01 00:00:00 | 2017-05-03 23:59:59 |
|  3 |    12 | 2017-01-01 00:00:00 | 2017-02-28 23:59:59 |
|  4 |    14 | 2017-01-01 00:00:00 | 2017-04-14 23:59:59 |
|  4 |    12 | 2017-04-15 00:00:00 | 2017-05-30 23:59:59 |
|  5 |    20 | 2017-01-01 00:00:00 | 2017-01-31 23:59:59 |
|  5 |    20 | 2017-03-01 00:00:00 | 2017-03-31 23:59:59 |
|  6 |    15 | 2017-01-01 00:00:00 | 2017-02-28 23:59:59 |
|  6 |    15 | 2017-04-01 00:00:00 | 2017-04-30 23:59:59 |
+----+-------+---------------------+---------------------+

总的来说，它本质上是确定两个日期之间的最佳价格。

我过去使用过这个表，并且能够用 C# 解决它，但这次我需要一个纯 TSQL 方法。

我已经经历了一些深层嵌套的 CTE，并且因为得到的结果远不及应有的结果而失去了理智。提前感谢任何可以提供帮助的人。

编辑:我什至搞砸了想要的结果，因为这太令人困惑了。固定(我认为)。

编辑2:示例:

+------+-------+-------------------------+-------------------------+
|  Id  | Price |        StartDate        |         EndDate         |
+------+-------+-------------------------+-------------------------+
| 8611 | 31.98 | 2017-06-06 00:00:00.000 | 2017-09-24 23:59:59.000 |
| 8611 | 31.98 | 2017-09-25 00:00:00.000 | 2017-12-31 23:59:59.000 |
| 8611 | 28.78 | 2017-07-31 00:00:00.000 | 2017-09-30 23:59:59.000 |
| 8611 | 28.78 | 2017-10-30 00:00:00.000 | 2017-12-31 23:59:59.000 |
+------+-------+-------------------------+-------------------------+

@GordonLinoff 的结果:

+------+-------+-------------------------+-------------------------+
|  Id  | Price |        StartDate        |         EndDate         |
+------+-------+-------------------------+-------------------------+
| 8611 | 28.78 | 2017-06-06 00:00:00.000 | 2017-12-31 23:59:59.000 |
+------+-------+-------------------------+-------------------------+

结果应该是:

+------+-------+-------------------------+-------------------------+
|  Id  | Price |        StartDate        |         EndDate         |
+------+-------+-------------------------+-------------------------+
| 8611 | 31.98 | 2017-06-06 00:00:00.000 | 2017-07-30 23:59:59.000 |
| 8611 | 28.78 | 2017-07-31 00:00:00.000 | 2017-09-30 23:59:59.000 |
| 8611 | 31.98 | 2017-10-01 00:00:00.000 | 2017-10-29 23:59:59.000 |
| 8611 | 28.78 | 2017-10-30 00:00:00.000 | 2017-12-31 23:59:59.000 |
+------+-------+-------------------------+-------------------------+

Answer 1

你有日历/日期表吗？如果是这样，那么您可以使用日期表来帮助您获得表中期间内每个日期的每种产品的最低价格。

之后，您可以通过查看具有相同产品 ID 的下一个和上一个记录来获取每个时期的开始和结束日期。您可以使用 LAG 和 LEAD 函数来执行此操作。这为您提供了每个所需组的外部边界。

从那里开始，只需稍微摆弄即可获得最终结果。我在下面提供了一个例子，它应该会给你你想要的结果。

--Get the best price per date for each product
WITH BestPricePerDate AS (
    SELECT 
        Id,
        MIN(Price) Price,
        c.[Date]
    FROM [YourTable] yt
        INNER JOIN dbo.Calendar c
            ON c.[Date] BETWEEN yt.StartDate AND yt.EndDate
    GROUP BY Id, [Date]
),
--Check whether the date is the start or the end of a period
PeriodsMarkedPerId AS(
    SELECT 
        Id,
        Price,
        [Date],
        CASE WHEN 
            ISNULL(LAG(Price,1) OVER (PARTITION BY Id ORDER BY [Date]),-1) <> Price 
            OR ISNULL(LAG([Date],1) OVER (PARTITION BY Id ORDER BY [Date]),'1999-01-01') <> DATEADD(DAY,-1,[Date]) THEN 1 ELSE 0 END IsStartDate,
        CASE WHEN 
            ISNULL(LEAD(Price,1) OVER (PARTITION BY Id ORDER BY [Date]),-1) <> Price 
            OR ISNULL(LEAD([Date],1) OVER (PARTITION BY Id ORDER BY [Date]),'1999-01-01') <> DATEADD(DAY,1,[Date]) THEN 1 ELSE 0 END IsEndDate
    FROM BestPricePerDate
),
--Keep only the start and end date records
PeriodStartAndEndDates AS(
    SELECT 
        Id, 
        Price,
        [Date],
        IsStartDate,
        IsEndDate
    FROM PeriodsMarkedPerId
    WHERE IsStartDate = 1 OR IsEndDate = 1
),
--Move StartDate and EndDate to one record
StartAndEndDatesOnSameRow AS(
    SELECT 
        Id, 
        Price, 
        [Date] AS StartDate,
        LEAD([Date],1) OVER (ORDER BY Id, [Date]) AS EndDate,
        IsStartDate
    FROM PeriodStartAndEndDates
)
--Get the resulting periods
SELECT Id, Price, StartDate, EndDate 
FROM StartAndEndDatesOnSameRow
WHERE IsStartDate = 1
ORDER BY Id, StartDate

如果您没有日期表，那么您可以轻松创建一个。网络上有很多这样的例子。

我希望这有帮助!