Question

我有一个包含职位描述栏和日期列的表。我想按照描述分组后得到每行的行号，如下所示。

 Description                     RunDate                    rn

File Cleanup             2013-12-30 00:00:00.0000000 +00:00 1
File Cleanup             2013-12-29 00:00:00.0000000 +00:00 2
Billing Extract          2013-12-30 00:00:00.0000000 +00:00 1
Billing Extract          2013-12-30 00:00:00.0000000 +00:00 2
Billing Extract          2013-12-29 00:00:00.0000000 +00:00 3
Unit Data Extract   2013-12-05 00:00:00.0000000 +00:00  1
Monthly Extract         2013-12-05 00:00:00.0000000 +00:00  1

我能够使用以下查询在SQL中实现此目的

SELECT [Description], RunDate, rn = ROW_NUMBER()
OVER (PARTITION BY [Description] ORDER BY RunDate DESC)
FROM BackgroundJobs

我无法将其转换为Linq to SQL。我尝试使用

var jobGroups = context.BackgroundJobs.GroupBy(g => new{g.Description, g.RunDate}).Select((jobs, index) => new { RowCount = index++, BackgroundJob = jobs }).Tolist();

输出

 Description                     RunDate                   rn

File Cleanup            2013-12-30 00:00:00.0000000 +00:00  1
File Cleanup            2013-12-29 00:00:00.0000000 +00:00  2
Billing Extract         2013-12-30 00:00:00.0000000 +00:00  3
Billing Extract         2013-12-30 00:00:00.0000000 +00:00  4
Billing Extract         2013-12-29 00:00:00.0000000 +00:00  5
Unit Data Extract   2013-12-05 00:00:00.0000000 +00:00  6
Monthly Extract         2013-12-05 00:00:00.0000000 +00:00  7

Linq to SQL查询增加了行号，但在描述更改时没有重置为1。

当组描述在linq中更改为SQL时，请告知如何将行号重置为1.

谢谢 Mahita

Answer 1

你很接近，但你必须更深一级地进行Select指数：

var jobGroups = 
    context.BackgroundJobs
           .GroupBy(job => new { job.Description, job.RunDate })
           .Select(g => new
            {
               g.Key, 
               Jobs = g.Select((job,i) => new
               { 
                  RowCount = i + 1,
                  job
               })
            })
           .Tolist();

在AsEnumerable()之前可能需要Select(g => ...，因为在LINQ到SQL后端的许多实现中，不支持Select的索引重载。

linq到每组的SQL行号

1 个答案: