在一个 LINQ 查询中获取两列的总和而不进行分组 [英] Get sum of two columns in one LINQ query without grouping

问题描述

我想在一个查询中总结一个表的三个不同字段.我想要一个相当于这个 T-SQL 的 linq:

I want to sum up three different fields of a table in one query. I want a linq equivalent of this T-SQL:

select sum(fld1), SUM(fld2),  SUM(fld3)   from MyTable where classID = 5

我发现的所有示例都使用 group by 或多次调用查询，每个需要汇总的字段一次.

All examples I have found either use a group by or call the query multiple times, once for each field that needs to be summed up.

我现在有这样的事情.但我不想在其中添加 group by 子句，因为它的 T-SQL 形式不需要它.

I have something like this now. But I don't want to add a group by clause to it as it is not required in its T-SQL form.

from a in MyTable
where a.classID == 5
group a by a.classID into g
select new 
{
Sumfld1 =  g.Sum(x => x.fld1 ), 
Sumfld2 = g.Sum(x => x.fld2),
Sumfld3 = g.Sum(x => x.fld3)
}

有什么建议吗?感谢您抽出宝贵时间.

Any suggestions? Thanks for your time.

推荐答案

事实证明，在 linq-to-sql 中，您可以通过以下方式实现:

As it turns out, in linq-to-sql you can get very close by doing:

from a in MyTable
where a.classID == 5
group a by 0 into g
select new 
{
    Sumfld1 = g.Sum(x => x.fld1), 
    Sumfld2 = g.Sum(x => x.fld2),
    Sumfld3 = g.Sum(x => x.fld3)
}

(注意0的分组)

它不会转换为 sql GROUP BY，而是来自子查询的多个 SUM 的 SELECT.就执行计划而言，它甚至可能是相同的.

It does not translate into a sql GROUP BY, but a SELECT of multiple SUMs from a subquery. In terms of execution plan it may even be the same.

Entity Framework 仍然创建一个 GROUP BY，尽管是通过 0.

Entity Framework still creates a GROUP BY, albeit by 0.

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