Question

假设下表......

ValueHistory ID int（身份）， HistoryDate日期时间， Contract_ID int， Item_ID int，价值小钱币

我想了解最新的Value（基于HistoryDate）以及与之关联的ID，按Contract_ID和Item_ID分组。

我目前有这个，它会显示最新的Date / Contract_ID / Item_ID，但显然我不能按ID分组，因为它会带回太多行。我考虑使用最大ID，但不幸的是，由于日期的插入方式，可能会有较低的ID，并且日期更近。

SELECT
    MAX([HistoryDate]) as 'Max_HistoryDate',
    [Contract_ID],
    [Item_ID]
FROM [ValueHistory]
WHERE 
        [HistoryDate] < @EndDate
GROUP BY [Item_ID], [Contract_ID]

我假设有一些方法可以通过一个额外的子查询来实现这一点，但它目前让我失望了。

SQL小提琴：http://sqlfiddle.com/#!18/655e9/1

按建议回答，效果很好。

select
    ID
    , HistoryDate
    , Contract_ID
    , Item_ID
from
(
    SELECT
        HistoryDate
        , ID
        , Contract_ID
        , Item_ID
        , RowNum = ROW_NUMBER() over(partition by Contract_ID, Item_ID order by HistoryDate DESC)
    FROM ValueHistory
    WHERE HistoryDate < @EndDate
) x
where x.RowNum = 1

Answer 1

很确定你想要这样的东西。

select HistoryDate
    , Contract_ID
    , Item_ID
from
(
    SELECT
        HistoryDate
        , Contract_ID
        , Item_ID
        , RowNum = ROW_NUMBER() over(partition by Contract_ID order by HistoryDate DESC)
    FROM ValueHistory
    WHERE HistoryDate < @EndDate
) x
where x.RowNum = 1

Answer 2

我会将结果重新加入原始表格，按照项目ID合约ID和与最长历史日期匹配的历史日期进行配对。

select *
from
(select *
from [ValueHistory]
) a
join
(
SELECT
    MAX([HistoryDate]) as [Max_HistoryDate],
    [Contract_ID] as [bContract_ID],
    [Item_ID] as [bItem_ID]
FROM [ValueHistory]
WHERE 
    [HistoryDate] < @EndDate
GROUP BY [Item_ID], [Contract_ID]) b

on a.[item_id]=b.[bitem_id] and
    a.[contract_id]=b.[bcontract_id] and
    a.[HistoryDate]=b.[Max_HistoryDate]

Answer 3

使用cte可能会有所帮助：

;with cte (Max_HistoryDate,Contract_ID,Item_ID) as
(
   SELECT
      MAX([HistoryDate]) as 'Max_HistoryDate',
      [Contract_ID],
      [Item_ID]
   FROM [ValueHistory]
   WHERE [HistoryDate] < '2018-02-01'
   GROUP BY [Item_ID], [Contract_ID]
)
Select Value, ih.Contract_ID, ih.Item_ID
From ValueHistory ih
inner join cte on ih.Contract_ID = cte.Contract_ID
               and ih.Item_ID = cte.Item_ID
where ih.HistoryDate = cte.Max_HistoryDate

SQL - 按最大日期分组加入（包括ID）

3 个答案: