9

我没想到会生成这样的查询...

放回去，如果我保留一个包含，查询看起来不错，它做了一个简单的左连接

询问：

using (var db = new Context())
{
    var data = db.MainTables.Include(x => x.LookupTables)
                            .Where(d => d.MainId == 10)
                            .FirstOrDefault();
}

生成的 SQL：

Opened connection at 2014-05-12 17:37:10 -04:00
SELECT 
    [Project1].[MainId] AS [MainId], 
    [Project1].[C1] AS [C1], 
    [Project1].[LookupId] AS [LookupId]
    FROM ( SELECT 
        [Limit1].[MainId] AS [MainId], 
        [Extent2].[LookupId] AS [LookupId], 
        CASE WHEN ([Extent2].[MainId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
        FROM   (SELECT TOP (1) [Extent1].[MainId] AS [MainId]
            FROM [dbo].[MainTable] AS [Extent1]
            WHERE 10 = [Extent1].[MainId] ) AS [Limit1]
        LEFT OUTER JOIN [dbo].[MainTable_LookupTable] AS [Extent2] ON [Limit1].[MainId] = [Extent2].[MainId]
    )  AS [Project1]
    ORDER BY [Project1].[MainId] ASC, [Project1].[C1] ASC
-- Executing at 2014-05-12 17:37:11 -04:00
-- Completed in 11 ms with result: SqlDataReader

Closed connection at 2014-05-12 17:37:11 -04:00

如果我有不止一个，查询会变得疯狂，UNION ALL...

这是预期的行为吗？如果是，是否可以在为所有这些使用多个简单的左连接时保留一个包含的行为？

模型：

数据库模型2

询问：

using (var db = new Context())
{
    var data = db.MainTables.Include(x => x.LookupTables)
                            .Include(x => x.MainTable_MoreData)
                            .Include(x => x.MaintTable_DataLookup)
                            .Include(x => x.MainTable_EvenMoreData)
                            .Where(d => d.MainId == 10)
                            .FirstOrDefault()

}

生成的 SQL：

Opened connection at 2014-05-12 18:00:56 -04:00
SELECT 
    [UnionAll3].[C2] AS [C1], 
    [UnionAll3].[C3] AS [C2], 
    [UnionAll3].[C4] AS [C3], 
    [UnionAll3].[C5] AS [C4], 
    [UnionAll3].[C6] AS [C5], 
    [UnionAll3].[C7] AS [C6], 
    [UnionAll3].[C8] AS [C7], 
    [UnionAll3].[C9] AS [C8], 
    [UnionAll3].[C10] AS [C9], 
    [UnionAll3].[C11] AS [C10], 
    [UnionAll3].[C12] AS [C11], 
    [UnionAll3].[C13] AS [C12], 
    [UnionAll3].[C1] AS [C13], 
    [UnionAll3].[C14] AS [C14], 
    [UnionAll3].[C15] AS [C15], 
    [UnionAll3].[C16] AS [C16], 
    [UnionAll3].[C17] AS [C17], 
    [UnionAll3].[C18] AS [C18], 
    [UnionAll3].[C19] AS [C19], 
    [UnionAll3].[C20] AS [C20], 
    [UnionAll3].[C21] AS [C21], 
    [UnionAll3].[C22] AS [C22], 
    [UnionAll3].[C23] AS [C23], 
    [UnionAll3].[C24] AS [C24], 
    [UnionAll3].[C25] AS [C25], 
    [UnionAll3].[C26] AS [C26], 
    [UnionAll3].[C27] AS [C27], 
    [UnionAll3].[C28] AS [C28], 
    [UnionAll3].[C29] AS [C29], 
    [UnionAll3].[C30] AS [C30], 
    [UnionAll3].[C31] AS [C31], 
    [UnionAll3].[C32] AS [C32], 
    [UnionAll3].[C33] AS [C33], 
    [UnionAll3].[C34] AS [C34], 
    [UnionAll3].[C35] AS [C35], 
    [UnionAll3].[C36] AS [C36], 
    [UnionAll3].[C37] AS [C37], 
    [UnionAll3].[C38] AS [C38], 
    [UnionAll3].[C39] AS [C39], 
    [UnionAll3].[C40] AS [C40], 
    [UnionAll3].[C41] AS [C41], 
    [UnionAll3].[C42] AS [C42], 
    [UnionAll3].[C43] AS [C43], 
    [UnionAll3].[C44] AS [C44], 
    [UnionAll3].[C45] AS [C45], 
    [UnionAll3].[C46] AS [C46], 
    [UnionAll3].[C47] AS [C47], 
    [UnionAll3].[C48] AS [C48], 
    [UnionAll3].[C49] AS [C49], 
    [UnionAll3].[C50] AS [C50], 
    [UnionAll3].[C51] AS [C51]
    FROM  (SELECT 
        [UnionAll2].[C1] AS [C1], 
        [UnionAll2].[C2] AS [C2], 
        [UnionAll2].[C3] AS [C3], 
        [UnionAll2].[C4] AS [C4], 
        [UnionAll2].[C5] AS [C5], 
        [UnionAll2].[C6] AS [C6], 
        [UnionAll2].[C7] AS [C7], 
        [UnionAll2].[C8] AS [C8], 
        [UnionAll2].[C9] AS [C9], 
        [UnionAll2].[C10] AS [C10], 
        [UnionAll2].[C11] AS [C11], 
        [UnionAll2].[C12] AS [C12], 
        [UnionAll2].[C13] AS [C13], 
        [UnionAll2].[C14] AS [C14], 
        [UnionAll2].[C15] AS [C15], 
        [UnionAll2].[C16] AS [C16], 
        [UnionAll2].[C17] AS [C17], 
        [UnionAll2].[C18] AS [C18], 
        [UnionAll2].[C19] AS [C19], 
        [UnionAll2].[C20] AS [C20], 
        [UnionAll2].[C21] AS [C21], 
        [UnionAll2].[C22] AS [C22], 
        [UnionAll2].[C23] AS [C23], 
        [UnionAll2].[C24] AS [C24], 
        [UnionAll2].[C25] AS [C25], 
        [UnionAll2].[C26] AS [C26], 
        [UnionAll2].[C27] AS [C27], 
        [UnionAll2].[C28] AS [C28], 
        [UnionAll2].[C29] AS [C29], 
        [UnionAll2].[C30] AS [C30], 
        [UnionAll2].[C31] AS [C31], 
        [UnionAll2].[C32] AS [C32], 
        [UnionAll2].[C33] AS [C33], 
        [UnionAll2].[C34] AS [C34], 
        [UnionAll2].[C35] AS [C35], 
        [UnionAll2].[C36] AS [C36], 
        [UnionAll2].[C37] AS [C37], 
        [UnionAll2].[C38] AS [C38], 
        [UnionAll2].[C39] AS [C39], 
        [UnionAll2].[C40] AS [C40], 
        [UnionAll2].[C41] AS [C41], 
        [UnionAll2].[C42] AS [C42], 
        [UnionAll2].[C43] AS [C43], 
        [UnionAll2].[C44] AS [C44], 
        [UnionAll2].[C45] AS [C45], 
        [UnionAll2].[C46] AS [C46], 
        [UnionAll2].[C47] AS [C47], 
        [UnionAll2].[C48] AS [C48], 
        [UnionAll2].[C49] AS [C49], 
        [UnionAll2].[C50] AS [C50], 
        [UnionAll2].[C51] AS [C51]
        FROM  (SELECT 
            [UnionAll1].[C1] AS [C1], 
            [UnionAll1].[MainId] AS [C2], 
            [UnionAll1].[MainId1] AS [C3], 
            [UnionAll1].[Field1] AS [C4], 
            [UnionAll1].[Field11] AS [C5], 
            [UnionAll1].[Field12] AS [C6], 
            [UnionAll1].[Field13] AS [C7], 
            [UnionAll1].[Field14] AS [C8], 
            [UnionAll1].[Field15] AS [C9], 
            [UnionAll1].[Field16] AS [C10], 
            [UnionAll1].[Field17] AS [C11], 
            [UnionAll1].[Field18] AS [C12], 
            [UnionAll1].[Field19] AS [C13], 
            [UnionAll1].[LookupId] AS [C14], 
            [UnionAll1].[Field161] AS [C15], 
            [UnionAll1].[Field151] AS [C16], 
            [UnionAll1].[Field141] AS [C17], 
            [UnionAll1].[Field131] AS [C18], 
            [UnionAll1].[Field121] AS [C19], 
            [UnionAll1].[Field111] AS [C20], 
            [UnionAll1].[Field110] AS [C21], 
            [UnionAll1].[C2] AS [C22], 
            [UnionAll1].[C3] AS [C23], 
            [UnionAll1].[C4] AS [C24], 
            [UnionAll1].[C5] AS [C25], 
            [UnionAll1].[C6] AS [C26], 
            [UnionAll1].[C7] AS [C27], 
            [UnionAll1].[C8] AS [C28], 
            [UnionAll1].[C9] AS [C29], 
            [UnionAll1].[C10] AS [C30], 
            [UnionAll1].[C11] AS [C31], 
            [UnionAll1].[C12] AS [C32], 
            [UnionAll1].[C13] AS [C33], 
            [UnionAll1].[C14] AS [C34], 
            [UnionAll1].[C15] AS [C35], 
            [UnionAll1].[C16] AS [C36], 
            [UnionAll1].[C17] AS [C37], 
            [UnionAll1].[C18] AS [C38], 
            [UnionAll1].[C19] AS [C39], 
            [UnionAll1].[C20] AS [C40], 
            [UnionAll1].[C21] AS [C41], 
            [UnionAll1].[C22] AS [C42], 
            [UnionAll1].[C23] AS [C43], 
            [UnionAll1].[C24] AS [C44], 
            [UnionAll1].[C25] AS [C45], 
            [UnionAll1].[C26] AS [C46], 
            [UnionAll1].[C27] AS [C47], 
            [UnionAll1].[C28] AS [C48], 
            [UnionAll1].[C29] AS [C49], 
            [UnionAll1].[C30] AS [C50], 
            [UnionAll1].[C31] AS [C51]
            FROM  (SELECT 
                CASE WHEN ([Join1].[MainId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1], 
                [Limit1].[MainId] AS [MainId], 
                [Limit1].[MainId] AS [MainId1], 
                [Limit1].[Field1] AS [Field1], 
                [Limit1].[Field11] AS [Field11], 
                [Limit1].[Field12] AS [Field12], 
                [Limit1].[Field13] AS [Field13], 
                [Limit1].[Field14] AS [Field14], 
                [Limit1].[Field15] AS [Field15], 
                [Limit1].[Field16] AS [Field16], 
                [Limit1].[Field17] AS [Field17], 
                [Limit1].[Field18] AS [Field18], 
                [Limit1].[Field19] AS [Field19], 
                [Join1].[LookupId1] AS [LookupId], 
                [Join1].[Field16] AS [Field161], 
                [Join1].[Field15] AS [Field151], 
                [Join1].[Field14] AS [Field141], 
                [Join1].[Field13] AS [Field131], 
                [Join1].[Field12] AS [Field121], 
                [Join1].[Field11] AS [Field111], 
                [Join1].[Field1] AS [Field110], 
                CAST(NULL AS int) AS [C2], 
                CAST(NULL AS int) AS [C3], 
                CAST(NULL AS varchar(1)) AS [C4], 
                CAST(NULL AS varchar(1)) AS [C5], 
                CAST(NULL AS varchar(1)) AS [C6], 
                CAST(NULL AS varchar(1)) AS [C7], 
                CAST(NULL AS varchar(1)) AS [C8], 
                CAST(NULL AS varchar(1)) AS [C9], 
                CAST(NULL AS varchar(1)) AS [C10], 
                CAST(NULL AS int) AS [C11], 
                CAST(NULL AS varchar(1)) AS [C12], 
                CAST(NULL AS varchar(1)) AS [C13], 
                CAST(NULL AS varchar(1)) AS [C14], 
                CAST(NULL AS varchar(1)) AS [C15], 
                CAST(NULL AS varchar(1)) AS [C16], 
                CAST(NULL AS varchar(1)) AS [C17], 
                CAST(NULL AS varchar(1)) AS [C18], 
                CAST(NULL AS int) AS [C19], 
                CAST(NULL AS int) AS [C20], 
                CAST(NULL AS int) AS [C21], 
                CAST(NULL AS varchar(1)) AS [C22], 
                CAST(NULL AS varchar(1)) AS [C23], 
                CAST(NULL AS varchar(1)) AS [C24], 
                CAST(NULL AS varchar(1)) AS [C25], 
                CAST(NULL AS varchar(1)) AS [C26], 
                CAST(NULL AS varchar(1)) AS [C27], 
                CAST(NULL AS varchar(1)) AS [C28], 
                CAST(NULL AS varchar(1)) AS [C29], 
                CAST(NULL AS varchar(1)) AS [C30], 
                CAST(NULL AS int) AS [C31]
                FROM   (SELECT TOP (1) [Extent1].[MainId] AS [MainId], [Extent1].[Field1] AS [Field1], [Extent1].[Field11] AS [Field11], [Extent1].[Field12] AS [Field12], [Extent1].[Field13] AS [Field13], [Extent1].[Field14] AS [Field14], [Extent1].[Field15] AS [Field15], [Extent1].[Field16] AS [Field16], [Extent1].[Field17] AS [Field17], [Extent1].[Field18] AS [Field18], [Extent1].[Field19] AS [Field19]
                    FROM [dbo].[MainTable] AS [Extent1]
                    WHERE 10 = [Extent1].[MainId] ) AS [Limit1]
                LEFT OUTER JOIN  (SELECT [Extent2].[MainId] AS [MainId], [Extent3].[LookupId] AS [LookupId1], [Extent3].[Field16] AS [Field16], [Extent3].[Field15] AS [Field15], [Extent3].[Field14] AS [Field14], [Extent3].[Field13] AS [Field13], [Extent3].[Field12] AS [Field12], [Extent3].[Field11] AS [Field11], [Extent3].[Field1] AS [Field1]
                    FROM  [dbo].[MainTable_LookupTable] AS [Extent2]
                    INNER JOIN [dbo].[LookupTable] AS [Extent3] ON [Extent3].[LookupId] = [Extent2].[LookupId] ) AS [Join1] ON [Limit1].[MainId] = [Join1].[MainId]
            UNION ALL
                SELECT 
                2 AS [C1], 
                [Limit2].[MainId] AS [MainId], 
                [Limit2].[MainId] AS [MainId1], 
                [Limit2].[Field1] AS [Field1], 
                [Limit2].[Field11] AS [Field11], 
                [Limit2].[Field12] AS [Field12], 
                [Limit2].[Field13] AS [Field13], 
                [Limit2].[Field14] AS [Field14], 
                [Limit2].[Field15] AS [Field15], 
                [Limit2].[Field16] AS [Field16], 
                [Limit2].[Field17] AS [Field17], 
                [Limit2].[Field18] AS [Field18], 
                [Limit2].[Field19] AS [Field19], 
                CAST(NULL AS int) AS [C2], 
                CAST(NULL AS varchar(1)) AS [C3], 
                CAST(NULL AS varchar(1)) AS [C4], 
                CAST(NULL AS varchar(1)) AS [C5], 
                CAST(NULL AS varchar(1)) AS [C6], 
                CAST(NULL AS varchar(1)) AS [C7], 
                CAST(NULL AS varchar(1)) AS [C8], 
                CAST(NULL AS varchar(1)) AS [C9], 
                [Extent5].[DataId] AS [DataId], 
                [Extent5].[MainId] AS [MainId2], 
                [Extent5].[SomeData] AS [SomeData], 
                [Extent5].[Field1] AS [Field110], 
                [Extent5].[Field11] AS [Field111], 
                [Extent5].[Field12] AS [Field121], 
                [Extent5].[Field13] AS [Field131], 
                [Extent5].[Field14] AS [Field141], 
                [Extent5].[Field15] AS [Field151], 
                CAST(NULL AS int) AS [C10], 
                CAST(NULL AS varchar(1)) AS [C11], 
                CAST(NULL AS varchar(1)) AS [C12], 
                CAST(NULL AS varchar(1)) AS [C13], 
                CAST(NULL AS varchar(1)) AS [C14], 
                CAST(NULL AS varchar(1)) AS [C15], 
                CAST(NULL AS varchar(1)) AS [C16], 
                CAST(NULL AS varchar(1)) AS [C17], 
                CAST(NULL AS int) AS [C18], 
                CAST(NULL AS int) AS [C19], 
                CAST(NULL AS int) AS [C20], 
                CAST(NULL AS varchar(1)) AS [C21], 
                CAST(NULL AS varchar(1)) AS [C22], 
                CAST(NULL AS varchar(1)) AS [C23], 
                CAST(NULL AS varchar(1)) AS [C24], 
                CAST(NULL AS varchar(1)) AS [C25], 
                CAST(NULL AS varchar(1)) AS [C26], 
                CAST(NULL AS varchar(1)) AS [C27], 
                CAST(NULL AS varchar(1)) AS [C28], 
                CAST(NULL AS varchar(1)) AS [C29], 
                CAST(NULL AS int) AS [C30]
                FROM   (SELECT TOP (1) [Extent4].[MainId] AS [MainId], [Extent4].[Field1] AS [Field1], [Extent4].[Field11] AS [Field11], [Extent4].[Field12] AS [Field12], [Extent4].[Field13] AS [Field13], [Extent4].[Field14] AS [Field14], [Extent4].[Field15] AS [Field15], [Extent4].[Field16] AS [Field16], [Extent4].[Field17] AS [Field17], [Extent4].[Field18] AS [Field18], [Extent4].[Field19] AS [Field19]
                    FROM [dbo].[MainTable] AS [Extent4]
                    WHERE 10 = [Extent4].[MainId] ) AS [Limit2]
                INNER JOIN [dbo].[MainTable_MoreData] AS [Extent5] ON [Limit2].[MainId] = [Extent5].[MainId]) AS [UnionAll1]
        UNION ALL
            SELECT 
            3 AS [C1], 
            [Limit3].[MainId] AS [MainId], 
            [Limit3].[MainId] AS [MainId1], 
            [Limit3].[Field1] AS [Field1], 
            [Limit3].[Field11] AS [Field11], 
            [Limit3].[Field12] AS [Field12], 
            [Limit3].[Field13] AS [Field13], 
            [Limit3].[Field14] AS [Field14], 
            [Limit3].[Field15] AS [Field15], 
            [Limit3].[Field16] AS [Field16], 
            [Limit3].[Field17] AS [Field17], 
            [Limit3].[Field18] AS [Field18], 
            [Limit3].[Field19] AS [Field19], 
            CAST(NULL AS int) AS [C2], 
            CAST(NULL AS varchar(1)) AS [C3], 
            CAST(NULL AS varchar(1)) AS [C4], 
            CAST(NULL AS varchar(1)) AS [C5], 
            CAST(NULL AS varchar(1)) AS [C6], 
            CAST(NULL AS varchar(1)) AS [C7], 
            CAST(NULL AS varchar(1)) AS [C8], 
            CAST(NULL AS varchar(1)) AS [C9], 
            CAST(NULL AS int) AS [C10], 
            CAST(NULL AS int) AS [C11], 
            CAST(NULL AS varchar(1)) AS [C12], 
            CAST(NULL AS varchar(1)) AS [C13], 
            CAST(NULL AS varchar(1)) AS [C14], 
            CAST(NULL AS varchar(1)) AS [C15], 
            CAST(NULL AS varchar(1)) AS [C16], 
            CAST(NULL AS varchar(1)) AS [C17], 
            CAST(NULL AS varchar(1)) AS [C18], 
            [Extent7].[MainId] AS [MainId2], 
            [Extent7].[Data] AS [Data], 
            [Extent7].[Field1] AS [Field110], 
            [Extent7].[Field11] AS [Field111], 
            [Extent7].[Field12] AS [Field121], 
            [Extent7].[Field14] AS [Field141], 
            [Extent7].[Field15] AS [Field151], 
            [Extent7].[Field13] AS [Field131], 
            [Extent7].[MainId] AS [MainId3], 
            CAST(NULL AS int) AS [C19], 
            CAST(NULL AS int) AS [C20], 
            CAST(NULL AS varchar(1)) AS [C21], 
            CAST(NULL AS varchar(1)) AS [C22], 
            CAST(NULL AS varchar(1)) AS [C23], 
            CAST(NULL AS varchar(1)) AS [C24], 
            CAST(NULL AS varchar(1)) AS [C25], 
            CAST(NULL AS varchar(1)) AS [C26], 
            CAST(NULL AS varchar(1)) AS [C27], 
            CAST(NULL AS varchar(1)) AS [C28], 
            CAST(NULL AS varchar(1)) AS [C29], 
            CAST(NULL AS int) AS [C30]
            FROM   (SELECT TOP (1) [Extent6].[MainId] AS [MainId], [Extent6].[Field1] AS [Field1], [Extent6].[Field11] AS [Field11], [Extent6].[Field12] AS [Field12], [Extent6].[Field13] AS [Field13], [Extent6].[Field14] AS [Field14], [Extent6].[Field15] AS [Field15], [Extent6].[Field16] AS [Field16], [Extent6].[Field17] AS [Field17], [Extent6].[Field18] AS [Field18], [Extent6].[Field19] AS [Field19]
                FROM [dbo].[MainTable] AS [Extent6]
                WHERE 10 = [Extent6].[MainId] ) AS [Limit3]
            INNER JOIN [dbo].[MaintTable_DataLookup] AS [Extent7] ON [Limit3].[MainId] = [Extent7].[MainId]) AS [UnionAll2]
    UNION ALL
        SELECT 
        4 AS [C1], 
        [Limit4].[MainId] AS [MainId], 
        [Limit4].[MainId] AS [MainId1], 
        [Limit4].[Field1] AS [Field1], 
        [Limit4].[Field11] AS [Field11], 
        [Limit4].[Field12] AS [Field12], 
        [Limit4].[Field13] AS [Field13], 
        [Limit4].[Field14] AS [Field14], 
        [Limit4].[Field15] AS [Field15], 
        [Limit4].[Field16] AS [Field16], 
        [Limit4].[Field17] AS [Field17], 
        [Limit4].[Field18] AS [Field18], 
        [Limit4].[Field19] AS [Field19], 
        CAST(NULL AS int) AS [C2], 
        CAST(NULL AS varchar(1)) AS [C3], 
        CAST(NULL AS varchar(1)) AS [C4], 
        CAST(NULL AS varchar(1)) AS [C5], 
        CAST(NULL AS varchar(1)) AS [C6], 
        CAST(NULL AS varchar(1)) AS [C7], 
        CAST(NULL AS varchar(1)) AS [C8], 
        CAST(NULL AS varchar(1)) AS [C9], 
        CAST(NULL AS int) AS [C10], 
        CAST(NULL AS int) AS [C11], 
        CAST(NULL AS varchar(1)) AS [C12], 
        CAST(NULL AS varchar(1)) AS [C13], 
        CAST(NULL AS varchar(1)) AS [C14], 
        CAST(NULL AS varchar(1)) AS [C15], 
        CAST(NULL AS varchar(1)) AS [C16], 
        CAST(NULL AS varchar(1)) AS [C17], 
        CAST(NULL AS varchar(1)) AS [C18], 
        CAST(NULL AS int) AS [C19], 
        CAST(NULL AS varchar(1)) AS [C20], 
        CAST(NULL AS varchar(1)) AS [C21], 
        CAST(NULL AS varchar(1)) AS [C22], 
        CAST(NULL AS varchar(1)) AS [C23], 
        CAST(NULL AS varchar(1)) AS [C24], 
        CAST(NULL AS varchar(1)) AS [C25], 
        CAST(NULL AS varchar(1)) AS [C26], 
        CAST(NULL AS int) AS [C27], 
        [Extent9].[LookupId] AS [LookupId], 
        [Extent9].[MainId] AS [MainId2], 
        [Extent9].[MoreMoreData] AS [MoreMoreData], 
        [Extent9].[Field17] AS [Field171], 
        [Extent9].[Field16] AS [Field161], 
        [Extent9].[Field15] AS [Field151], 
        [Extent9].[Field14] AS [Field141], 
        [Extent9].[Field13] AS [Field131], 
        [Extent9].[Field12] AS [Field121], 
        [Extent9].[Field11] AS [Field111], 
        [Extent9].[Field1] AS [Field110], 
        [Extent9].[MainId] AS [MainId3]
        FROM   (SELECT TOP (1) [Extent8].[MainId] AS [MainId], [Extent8].[Field1] AS [Field1], [Extent8].[Field11] AS [Field11], [Extent8].[Field12] AS [Field12], [Extent8].[Field13] AS [Field13], [Extent8].[Field14] AS [Field14], [Extent8].[Field15] AS [Field15], [Extent8].[Field16] AS [Field16], [Extent8].[Field17] AS [Field17], [Extent8].[Field18] AS [Field18], [Extent8].[Field19] AS [Field19]
            FROM [dbo].[MainTable] AS [Extent8]
            WHERE 10 = [Extent8].[MainId] ) AS [Limit4]
        INNER JOIN [dbo].[MainTable_EvenMoreData] AS [Extent9] ON [Limit4].[MainId] = [Extent9].[MainId]) AS [UnionAll3]
    ORDER BY [UnionAll3].[C3] ASC, [UnionAll3].[C1] ASC
-- Executing at 2014-05-12 18:00:57 -04:00
-- Completed in 39 ms with result: SqlDataReader

sql server 结果

dbresult2

为什么 8 行 2 就足够了？

此数据库示例未使用索引等进行优化，但这是执行计划

计划

理想情况下，我想生成一个看起来像这样的查询，同时保持实体框架跟踪更改，因为我将使用对象来更新数据库

SELECT        dbo.MainTable.MainId, dbo.MainTable.Field1, dbo.MainTable.Field11, dbo.MainTable.Field12, dbo.MainTable.Field13, dbo.MainTable.Field14, 
                         dbo.MainTable.Field15, dbo.MainTable.Field16, dbo.MainTable.Field17, dbo.MainTable.Field18, dbo.MainTable.Field19, dbo.MainTable_EvenMoreData.LookupId, 
                         dbo.MainTable_EvenMoreData.MainId AS Expr1, dbo.MainTable_EvenMoreData.MoreMoreData, dbo.MainTable_EvenMoreData.Field17 AS Expr2, 
                         dbo.MainTable_EvenMoreData.Field16 AS Expr3, dbo.MainTable_EvenMoreData.Field15 AS Expr4, dbo.MainTable_EvenMoreData.Field14 AS Expr5, 
                         dbo.MainTable_EvenMoreData.Field13 AS Expr6, dbo.MainTable_EvenMoreData.Field12 AS Expr7, dbo.MainTable_EvenMoreData.Field11 AS Expr8, 
                         dbo.MainTable_EvenMoreData.Field1 AS Expr9, dbo.MainTable_LookupTable.MainId AS Expr10, dbo.MainTable_LookupTable.LookupId AS Expr11, 
                         dbo.MainTable_MoreData.DataId, dbo.MainTable_MoreData.MainId AS Expr12, dbo.MainTable_MoreData.SomeData, dbo.MainTable_MoreData.Field1 AS Expr13, 
                         dbo.MainTable_MoreData.Field11 AS Expr14, dbo.MainTable_MoreData.Field12 AS Expr15, dbo.MainTable_MoreData.Field13 AS Expr16, 
                         dbo.MainTable_MoreData.Field14 AS Expr17, dbo.MainTable_MoreData.Field15 AS Expr18, dbo.MaintTable_DataLookup.MainId AS Expr19, 
                         dbo.MaintTable_DataLookup.Data, dbo.MaintTable_DataLookup.Field1 AS Expr20, dbo.MaintTable_DataLookup.Field11 AS Expr21, 
                         dbo.MaintTable_DataLookup.Field12 AS Expr22, dbo.MaintTable_DataLookup.Field14 AS Expr23, dbo.MaintTable_DataLookup.Field15 AS Expr24, 
                         dbo.MaintTable_DataLookup.Field13 AS Expr25
FROM            dbo.MainTable LEFT OUTER JOIN
                         dbo.MainTable_EvenMoreData ON dbo.MainTable.MainId = dbo.MainTable_EvenMoreData.MainId LEFT OUTER JOIN
                         dbo.MainTable_LookupTable ON dbo.MainTable.MainId = dbo.MainTable_LookupTable.MainId LEFT OUTER JOIN
                         dbo.MainTable_MoreData ON dbo.MainTable.MainId = dbo.MainTable_MoreData.MainId LEFT OUTER JOIN
                         dbo.MaintTable_DataLookup ON dbo.MainTable.MainId = dbo.MaintTable_DataLookup.MainId
WHERE dbo.MainTable.MainId = 10
4

2 回答 2

6

所以在玩了几个小时之后，我用一个简单的左连接和实体框架所做的巨大查询在 sql server 上做了一些负载平衡/执行计划/统计。

似乎实体框架大获全胜。

我将实施 .include() 解决方案。

于 2014-05-13T00:36:18.470 回答
2

是的，这很正常。实体框架正在使用您的（通常是分层的）关系模型并尝试生成一个查询，该查询将在一个大的平面表中生成所有必要的数据。

是否可以在为所有这些使用多个简单的左连接时保留一个包含的行为？

这取决于你所说的“行为”是什么意思。如果您的意思是生成类似的 SQL 查询，那么不，您不能。但是必须问你为什么关心这些查询：这些查询可能针对 SQL Server 进行了优化，但不会针对人类可读性进行优化。

如果您的意思是想要获得更好的性能，除了在一个大型数据库往返中急切加载所有内容之外，您还可以使用其他策略。我发现一种行之有效的策略是对每个关系使用新的往返，如下所示：

var dataQuery = db.MainTables.Where(d => d.MainId == 10);
var data = dataQuery.FirstOrDefault();
dataQuery.Select(x => x.MainTable_MoreData).ToList();
// etc.

这是一个简单的实用程序类，您可以使用它来减少繁琐，尤其是在从多个关系中加载数据时：

/// <summary>
/// This class aids in loading a lot of related data in Entity Framework.
/// <para>
/// Typically Entity Framework either lets you load entities Eagerly or Lazily,
/// but neither case handles things very well once you are adding many chained
/// relationships. A more ideal approach in these cases is to load all of the
/// entities you are going to need for a given relationship in a single round-trip, 
/// and do this once for every relationship you're interested in.
/// That's what this class helps with.
/// </para>
/// <para>
/// To use: simply create an EntityRelationshipLoader with the initial 
/// Entity-Framework-backed queryable that will be the basis of all the data
/// you're going to be loading. Then for each entity you want to load in relationship
/// to that original data type, call either <see cref="Include{TProp}"/> or
/// <see cref="IncludeMany{TProp}"/>. The return value from calling these methods may
/// be retained and used to include other property relationships based on the
/// property that you just defined. Each call to any of these methods will produce a
/// single round-trip.
/// </para>
/// <remarks>
/// Remember that all actions on the loader, including its original
/// construction, must be performed while the query's Entity Framework context
/// is active.
/// </remarks>
/// </summary>
/// <typeparam name="T"></typeparam>
public class EntityRelationshipLoader<T> : IRelationshipPropertyBuilder<T>
{
    private readonly IQueryable<T> _src;

    public EntityRelationshipLoader(IQueryable<T> src) : this(src, true)
    {
    }

    private EntityRelationshipLoader(IQueryable<T> src, bool evaluateSource)
    {
        _src = src;
        if (evaluateSource)
        {
            LoadEntities(src);
        }
    }

    public IRelationshipPropertyBuilder<TProp> IncludeMany<TProp>(Expression<Func<T, IEnumerable<TProp>>> navProp)
    {
        LoadEntities(_src.Select(navProp));
        return new EntityRelationshipLoader<TProp>(_src.SelectMany(navProp), false);
    }

    public IRelationshipPropertyBuilder<TProp> Include<TProp>(Expression<Func<T, TProp>> navProp)
    {
        return new EntityRelationshipLoader<TProp>(_src.Select(navProp), true);
    }

    /// <summary>
    /// Simple helper method to cause the given query to be executed, 
    /// thereby loading all the entities the query represents.
    /// </summary>
    /// <param name="query"></param>
    private void LoadEntities<T1>(IQueryable<T1> query)
    {
#pragma warning disable 168
        foreach (var item in query)
        {
        }
#pragma warning restore 168
    }

这将允许你说：

var dataQuery = db.MainTables.Where(d => d.MainId == 10);
var dataLoader = new EntityRelationshipLoader<MainTable>(dataQuery);
dataLoader.Include(x => x.LookupTables);
dataLoader.IncludeMany(x => x.MainTable_MoreData)
    // Do you need to load MoreData's .LookupTables properties?
    .Include(x => x.LookupTables);
dataLoader.Include(x => x.MaintTable_DataLookup)
dataLoader.Include(x => x.MainTable_EvenMoreData);
var data = dataQuery.Single(); // Or ToList() if you need multiple of them.
于 2014-05-12T21:53:29.793 回答