如何只获取最大行数的记录？

Question

以下查询结果记录如下。

如何仅获取记录的最大行数？我已经对该查询进行了20,000条以上的记录，以识别重复项并获取最新日期及其处理的数量（RowNumber）。

select [FileName], ProcessDate,
ROW_NUMBER() over (partition by [FileName] order by [FileName] desc) RowNumber 
from  StagingTable
where filename = 'abc.txt'

Answer 1

您要寻找过滤器吗？

select s.*
from (select [FileName], ProcessDate,
             ROW_NUMBER() over (partition by [FileName] order by ProcessDate desc) as RowNumber 
      from StagingTable
      where filename = 'abc.txt'
     ) s
where RowNumber = 1;

请注意，ORDER BY已更改。

如果您还需要总数，则将其添加为附加列：

select s.*
from (select [FileName], ProcessDate,
             count(*) over (partition by filename) as cnt,
             ROW_NUMBER() over (partition by [FileName] order by ProcessDate desc) as RowNumber 
      from StagingTable
      where filename = 'abc.txt'
     ) s
where RowNumber = 1;

Answer 2

根据您的逻辑，似乎没有最大行数。还是行号绑定到ProcessDate以外的其他字段？

据我了解您的问题，我将使用以下查询：

SELECT [FileName], MAX([ProcessDate]) AS [ProcessDate], COUNT(*) AS [Count]
FROM [StagingTable]
GROUP BY [FileName]

Answer 3

您的查询有一个错误：您在OrderBy中写了FileName，但是我想您使用的是日期。

您可以在ROW_NUMBER（）列上加倍：

WITH VersionSorting AS (
  select
    [FileName],
    ProcessDate,
    ROW_NUMBER() over (partition by [FileName] order by [ProcessDate] ASC) FileVersion,
    ROW_NUMBER() over (partition by [FileName] order by [ProcessDate] DESC) FileVersionInv
  from  StagingTable
)
SELECT FileName, ProcessDate, FileVersion
FROM VersionSorting
WHERE FileVersionInv = 1
-- AND FileName = 'abc.txt'