如何在sql server中获得负rownumber

Question

我有一组带有DateTime的数据，比如说CalculatedOn我想要的是从当前日期getdate()开始，并获得当前日期之前的x量记录，以及之后的相同数量。

如果x = 50那么现在前50，现在前50。 我当时认为rownumber()对于这个来说是完美的，但是我想不出如何将前面的行数为负数而将来为正数。

还有一个问题是，如果没有50个先前或将来会发生什么，但那将会发生。

假设该表只有两列：

create table MyTable
(
   Id int not null constraint pk_mytable primary key,
   SomeTextIWant nvarchar(50) not null,
   CalculateDate DateTime not null
);

结果：

如果今天是25/04 12:54

然后

Id, SomeTextIWant, CalculatedDate
-- 50 from before now--
-----now here-----
-- 50 from after now--

Answer 1

如果你想在之前和之后获得50行，也许这会做你想要的：

with cte1 as (
      select top 50 t.*
      from table t
      where CalculatedDate <= getdate()
      order by CalculatedDate desc
     ),
     cte2 as (
      select top 50 t.*
      from table t
      where CalculatedDate > getdate()
      order by CalculatedDate
     )
select *
from (select * from cte1 union all select * from cte2) t

编辑：

从问题的上下文中我不清楚是否确实需要行号。 很容易添加，thoug：

(select top 50 t.*,
        - row_number() over (order by CalculatedDate desc) as rownumber
 from table t
 where CalculatedDate <= getdate()
 order by CalculatedDate desc
)
union all
(select top 50 t.*,
        row_number() over (order by CalculatedDate) as rownumber
 from table t
 where CalculatedDate > getdate()
 order by CalculatedDate
)

您实际上可以将这些组合成一个查询：

select t.*,
       ((case when CalculatedDate < getdate() then -1 else 1 end) *
        (row_number() over (partition by (case when CalculatedDate < getdate() then 1 else 0 end)
                           order by (case when CalculatedDate < getdate() then CalculatedDate end) desc, 
                                     CalculatedDate asc
                           )
         )) as rn
from table t;

您可以将其放在子查询中并选择-50到50之间的rn 。

但是，我不确定如何处理第0行，并且该问题没有提供有关如何处理与getdate()匹配的任何记录的信息（尽管不太可能）。 我认为第一个答案是OP需要的。

Answer 2

您可以使用两个CTE，一个用于过去，一个用于将来的日期，然后将ROW_NUMBER与ASC和DESC ，在此之前乘以-1并连接所有：

WITH dataBefore AS
(
    SELECT d.*, rn = (-1) * row_Number() over (Order By CalculatedOn DESC)
    FROM dbo.TableName d
    WHERE CalculatedOn < GetDate()
)
, dataAfter AS
(
    SELECT d.*, rn = row_Number() over (Order By CalculatedOn ASC)
    FROM dbo.TableName d
    WHERE CalculatedOn >= GetDate()
)
SELECT * FROM
(
    SELECT db.*
    FROM dataBefore db
    UNION ALL 
    SELECT da.*
    FROM dataAfter da
)x
WHERE x.rn >= -50 AND x.RN <= 50
ORDER BY x.RN

Answer 3

试试这个...

With myCte
As
(
    Select top 2 column1,column2 from  YourTable where yourdate > '2014-04-23'
    union 
    Select top 2 column1,column2 from  YourTable where yourdate  < '2014-04-23'
) select ROW_NUMBER() over (order by column1) as RNO,* from myCte

Answer 4

使用RowNumber

SELECT TOP 50 ROW_NUMBER() OVER (ORDER BY CalculateDate) AS RowNum,
    id, SomeTextIWant, CalculateDate
FROM MyTable
WHERE CalculateDate > @Date

UNION ALL

SELECT TOP 50 -ROW_NUMBER() OVER (ORDER BY CalculateDate DESC) AS RowNum,
    id, SomeTextIWant, CalculateDate
FROM MyTable
WHERE CalculateDate < @Date