Question

我尝试将EntityFramework 6生成的SQL重用为手动创建的SQL语句中的子选择。例如，以下查询：

dbContext.Users
     .GroupBy(u => u.Email)
     .Select(g => new {Email = u.Key, Name = g.Max(u1 => u1.Name)})
     .ToString()

以下SQL中的结果：

SELECT 
1 AS [C1], 
[GroupBy1].[K1] AS [Email], 
[GroupBy1].[A1] AS [C2]
FROM ( SELECT 
    [Extent1].[Email] AS [K1], 
    MAX([Extent1].[Name]) AS [A1]
    FROM [dbo].[Users] AS [Extent1]
    GROUP BY [Extent1].[Email]
)  AS [GroupBy1]

请注意，select中的字段列表与查询返回的数据类型不匹配（有一个C1，C2不是{Email，Name}的匿名类型）。有没有办法通过查看查询属性/等来找出映射？然后，我将能够在外部SQL语句中引用这些属性。

Answer 1

你最好手动编码。这是一个完整的例子：

CREATE TABLE #Users (Email varchar(200), Name varchar(200))

INSERT INTO #Users (Email, Name) VALUES ('vold@stack.com', 'Vololdymyr 1')
INSERT INTO #Users (Email, Name) VALUES ('vold@stack.com', 'Vololdymyr 2')

SELECT u.Email, MAX(u.Name) As Name FROM #Users u GROUP BY Email

DROP TABLE #Users

结果是：

Email               Name
---------------------------------
vold@stack.com      Vololdymyr 2

EF生成的SQL和属性映射/投影

1 个答案: