如何在LINQ中使用分区？

Question

我对如何将此查询更改为LINQ感到困惑

  select 
     CONTENT
  from
     (    
        select 
           CONTENT,
           CAM_ID,
           max(CAM_ID) over (partition by DOCUMENT_ID) MAX_ID
        from    
           T_CAM_REVISION
        where 
           DOCUMENT_ID = '101'
     )
  where     
     CAM_ID = MAX_ID

所以我可以获得单一的内容价值.

Answer 1

在LINQ中没有办法做max(...) over (...)。这是一个等效的查询：

var maxCamID =
    context.T_CAM_REVISION
    .Where(rev => rev.DOCUMENT_ID == "101")
    .Max(rev => rev.CAM_ID);

var query =
    from rev in context.T_CAM_REVISION
    where rev.CAM_ID == maxCamID
    where rev.DOCUMENT_ID == "101"
    select rev.CONTENT;

如果您只想要一个结果：

var result =
    context.T_CAM_REVISION
    .First(rev => rev.CAM_ID == maxCamID
               && rev.DOCUMENT_ID == "101")
    .CONTENT;