Linq to SQL:如何在没有分组的情况下进行聚合? [英] Linq to SQL: how to aggregate without a group by?

问题描述

我正在搜索与此查询等效的 Linq-to-SQL:

I am searching for the Linq-to-SQL equivalent to this query:

SELECT
  [cnt]=COUNT(*),
  [colB]=SUM(colB),
  [colC]=SUM(colC),
  [colD]=SUM(colD)
FROM myTable

这是没有 group by 的聚合.除了发出四个单独的查询(一个计数和三个总和)之外，我似乎找不到任何方法来做到这一点.有什么想法吗?

This is an aggregate without a group by. I can't seem to find any way to do this, short of issuing four separate queries (one Count and three Sum). Any ideas?

推荐答案

这就是我发现的，好像你仍然需要做一个 group by...可以只使用常量:

This is what I found seems like you still have to do a group by...can just use constant:

var orderTotals =
    from ord in dc.Orders
    group ord by 1 into og
    select new
    {
        prop1 = og.Sum(item=> item.Col1),
        prop2 = og.Sum(item => item.Col2),
        prop3 = og.Count(item => item.Col3)
    };

这会产生以下 SQL，这不是最佳的，但有效:

This produces the following SQL, which is not optimal, but works:

SELECT SUM([Col1]) as [prop1], SUM([Col2]) as [prop2], COUNT(*) AS [prop3]
FROM (
    SELECT 1 AS [value], [t0].[Col1], [t0].[Col2], [t0].[Col3]
    FROM [table] AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]

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