需要獲得一個ID的最小值和最大值日期與分鐘（日期）和max（日期）datavalue在考慮這個數據在同一列

Question

一個datavalue：

ID  FirstDate  LastDate  ItemId 
12A  05-11-2011  05-11-2011  0 
12A  12-19-2011  12-19-2011  3 
12A  01-04-2012  01-04-2012  3 
12A  01-19-2012  01-19-2012  12 
64B  06-15-2010  06-15-2010  0 
64B  08-19-2011  08-19-2011  3 

我想看看：

ID  FirstDate FirstItemId  LastDate  LastItemId 
12A 05-11-2011  0   01-19-2012  12 
64B 06-15-2010  0   08-19-2011  3 

Answer 1

在它的最基本的形式，你可能會想在SQL min and group by功能結合起來：

select ID 
    , min(FirstDate) as FirstDate 
    , min(ItemId) as FirstItemId 
    , max(LastDate) as LastDate 
    , max(ItemId) as LastItemId 
from MyTable 
group by ID 

注意，howeve r，這將返回每列的絕對最小值和最大值，不一定與FirstDate相對應的ItemId等，除非數據碰巧是這樣。這裏是一個可能的替代方案，要獲得基於第一/最後日期ItemIDs：

-- Get ItemIDs that correspond to First/Last Dates 
select ID 
    , FirstDate 
    , (select min(ItemID) from Mytable where ID = a.ID and FirstDate = a.FirstDate) as FirstItemID 
    , LastDate 
    , (select max(ItemID) from Mytable where ID = a.ID and LastDate = a.LastDate) as LastItemID 
from (
    select ID 
     , min(FirstDate) as FirstDate 
     , max(LastDate) as LastDate 
    from Mytable 
    group by ID 
) as a 

我發現，相關子查詢往往比窗口函數（也可能更容易理解）更快，但你必須測試中你的環境與你的數據。

Answer 2

您可以使用窗口函數的組合來得到這樣的結果：

select id, 
    max(case when FirstRowNumber= 1 then firstdate end) firstdate, 
    max(case when FirstRowNumber= 1 then itemid end) firstitemId, 
    max(case when LastRowNumber= 1 then lastdate end) lastdate, 
    max(case when LastRowNumber= 1 then itemid end) lastitemId 
from 
(
    select id, firstdate, lastdate, itemid, 
    row_number() over(partition by id order by firstdate) FirstRowNumber, 
    row_number() over(partition by id order by lastdate desc) LastRowNumber 
    from yourtable 
) x 
where FirstRowNumber= 1 
    or LastRowNumber= 1 
group by id 

見SQL Fiddle with Demo。

此解決方案將row_number分配給ASC/DESC日期順序中的記錄。那麼你只關心row_number = 1的記錄。然後我應用了一個聚合和一個CASE聲明來獲得正確的結果。

或者你可以使用一個非常難看UNPIVOT和PIVOT解決方案：

select * 
from 
(
    select id, 
    val, 
    case when firstrownumber = 1 and col = 'firstdate' 
      then 'firstdate' 
     when firstrownumber = 1 and col = 'itemid' 
      then 'firstitemid' 
     when LastRowNumber = 1 and col = 'lastdate' 
      then 'lastdate' 
     when LastRowNumber = 1 and col = 'itemid' 
      then 'lastitemid' 
     else '' end col 
    from 
    (
    select id, 
     convert(varchar(10), firstdate, 120) firstdate, 
     convert(varchar(10), lastdate, 120) lastdate, 
     cast(itemid as varchar(10)) itemid, 
     row_number() over(partition by id order by firstdate) FirstRowNumber, 
     row_number() over(partition by id order by lastdate desc) LastRowNumber 
    from yourtable 
) x 
    unpivot 
    (
    val for col in (firstdate, lastdate, itemid) 
) u 
) x1 
pivot 
(
    max(val) 
    for col in ([firstdate], [firstitemid], 
       [lastdate], [lastitemid]) 
) p 

見SQL Fiddle with Demo