在C#LINQ中实现RANK OVER SQL子句 [英] Implementing RANK OVER SQL Clause in C# LINQ

问题描述

我需要实现以下T-SQL子句....

I need to implement the following T-SQL clause ....

RANK() OVER (PARTITION BY a.CategoryKey ORDER BY (x.Rate * @BASE_RATE ) DESC )as Rank

...在C#LINQ中.到目前为止，我想出的是类似....

...in C# LINQ. So far what I've come up with is something like ....

var rank = data.GroupBy(d => d.CategoryKey)
               .Select(group => group.OrderByDescending(g => g.Rate * @BAES_RATE) 

我认为，这将给我每个按速率* BASE_RATE排序的等级分区.但是我真正需要的是单行的个人排名，这是更大结果中的子查询.所以实际上我正在使用的完整SQL查询就像....

I think this would give me each rank partition ordered by rate * BASE_RATE. But what I actually need is the individual rank of a single row, with this being a subquery within a larger result. So really the full SQL query I'm working from is something like ....

SELECT 
    a.Rate,
    a.CategoryKey,
    a.ID,
    .
    .
    .
    RANK() OVER (PARTITION BY a.CategoryKey ORDER BY (x.Rate * @BASE_RATE ) DESC )as Rank
FROM data

推荐答案

如果您不需要确切的排名语义(即并列排名). 您可以使用精选投影可用的索引

If you don't need the exact Rank semantics (i.e. tied ranks). You can use the index available with select projections

var rank = data.GroupBy(d => d.CategoryKey)
               .SelectMany(g => g.OrderByDescending(y => y.Rate * @BAES_RATE)              
                                 .Select((x,i) => new{g.Key, Item=x, Rank=i+1}))

否则，您可以查看此答案

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