如何使用SQL Server获取max（date）的行记录？

Question

我有两个表，分别为TableNumber and TableDetails

TableNumber

ItemID  TableDetailsID   Qty
----------------------------
111     12121             5
111     12121            20 
112     12121            10
123     12121             5

111     22121            25
111     22121            25
123     22121            2

TableDetails

ID       placed   TableDetailsNumber    Date
--------------------------------------------------
12121    London    555                  2017-05-31
22121    Dubai     556                  2017-07-31   <-- Max Date of Item 111

预期产量

ItemID    Placed    TableDetailsNumber    Date         Qty
----------------------------------------------------------
111       Dubai     556                  2017-07-31    50    //(25 + 25) of 22121
112       London    555                  2017-05-31    10
123       Dubai     556                  2017-07-31     2

我试图做MAX（Date），但是我不能使用分组来Placed,TableDetails列

以及我不怎么用相同的TableDetailsNumber来求和ItemID的数量

请给我解释你的答案，以了解 ，谢谢

Answer 1

Row_number()是一个排序窗口函数，它将为partition by中的每个给定列集partition by分配一个数字，该数字从1开始， order by的order by 。

如果我们partition by ItemId并按order by Date desc则每个ItemId具有最新Date的行的row_number()为1 。

这样，我们可以使用子查询， 公共表表达式或top with ties过滤联接和聚合的结果。

使用top with ties和row_number() top with ties ：

select top 1 with ties
    tn.ItemId
  , td.Placed 
  , td.TableDetailsNumber
  , td.Date
  , Qty = sum(tn.Qty)
from TableNumber tn
  inner join TableDetails td
    on tn.TableDetailsId = td.Id
group by
    tn.ItemId
  , td.Placed 
  , td.TableDetailsNumber
  , td.Date
order by row_number() over (partition by tn.ItemId order by td.Date desc);

---

或带有row_number()的公用表表达式

;with cte as (
select 
    tn.ItemId
  , td.Placed 
  , td.TableDetailsNumber
  , td.Date
  , Qty = sum(tn.Qty)
  , rn = row_number() over (partition by tn.ItemId order by td.Date desc)
from TableNumber tn
  inner join TableDetails td
    on tn.TableDetailsId = td.Id
group by
    tn.ItemId
  , td.Placed 
  , td.TableDetailsNumber
  , td.Date
)
select ItemId, Placed, TableDetailsNumber, Date, Qty 
from cte
where rn = 1;

---

使用cross apply()另一种选择：

select
    i.ItemId
  , x.Placed 
  , x.TableDetailsNumber
  , x.Date
  , x.Qty 
from (select distinct ItemId from TableNumber) i
  cross apply (
    select top 1
        tn.ItemId
      , td.Placed 
      , td.TableDetailsNumber
      , td.Date
      , Qty = sum(tn.Qty)
    from TableNumber tn
      inner join TableDetails td
        on tn.TableDetailsId = td.Id
    where tn.ItemId = i.Itemid
    group by
        tn.ItemId
      , td.Placed 
      , td.TableDetailsNumber
      , td.Date
    order by td.Date desc
    ) x

extrester演示： http ：//rextester.com/QNV39265

每次回报：

+--------+--------+--------------------+------------+-----+
| ItemId | Placed | TableDetailsNumber |    Date    | Qty |
+--------+--------+--------------------+------------+-----+
|    111 | Dubai  |                556 | 2017-07-31 |  50 |
|    112 | London |                555 | 2017-05-31 |  10 |
|    123 | Dubai  |                556 | 2017-07-31 |   2 |
+--------+--------+--------------------+------------+-----+

Answer 2

这似乎将返回您想要的结果：

select n.itemid, d.placed, d.TableDetailsNumber, d.date, sum(n.qty)
from tablenumber n join
     tabledetails d
     on n.TableDetailsId = d.TableDetailsId
group by n.itemid, d.placed, d.TableDetailsNumber;

但这没有得到最新日期。 为了那个原因：

select nd.*
from (select n.itemid, d.placed, d.TableDetailsNumber, d.date, sum(n.qty),
             max(d.date) over (partition by n.itemid) as maxdate
      from tablenumber n join
           tabledetails d
           on n.TableDetailsId = d.TableDetailsId
      group by n.itemid, d.placed, d.TableDetailsNumber
     ) nd
where date = maxdate;

Answer 3

您也可以进行内部联接。 我包括了所有表创建代码，以复制测试用例并证明其准确性。

表创建和插入

CREATE TABLE TableNumber (ItemID INT, TableDetailsID INT, Qty INT)
CREATE TABLE TableDetails (ID INT, placed VARCHAR(25), TableDetailsNumber INT, DetailsDate Date)


INSERT INTO TableNumber 
    values 
     (111,12121,5),
     (111,12121,20),
     (112,12121,10),
     (123,12121,5),
     (111,22121,25),
     (111,22121,25),
     (123,22121,2)

INSERT INTO TableDetails 
    values 
     (12121,'London',555,'2017-05-31'),
     (22121,'Dubai',556,'2017-07-31')

询问

SELECT
     TN.ItemID
    ,TD.Placed
    ,TD.TableDetailsNumber
    ,MaxTable.maxDate
    ,Sum(TN.Qty) 'Qty'
FROM TableNumber TN
JOIN TableDetails TD 
    on TD.ID = TN.TableDetailsID
JOIN (
        SELECT 
         ItemID
        ,max(TD.DetailsDate) maxDate
        FROM TableNumber TN
        JOIN TableDetails TD 
            on TD.ID = TN.TableDetailsID
        GROUP BY 
         ItemID
        ) as MaxTable
    on MaxTable.maxDate = TD.DetailsDate
    and MaxTable.ItemID = TN.ItemID
GROUP BY 
     tn.ItemId
  , td.Placed 
  , td.TableDetailsNumber
  , MaxTable.maxDate