1

我有以下代码：

var comp = db.Companies.Select(x => new
        {

            topid = x.ID_comp,
            hill = ((from company in db.Companies
                    where x.ID_comp > company.ID_comp
                    orderby company.ID_comp
                    select new { h = company.ID_comp.ToString() })
                    .Concat((
                    from company in db.Companies
                    where x.ID_comp > company.ID_comp
                    orderby company.ID_comp descending
                    select new { h = company.ID_comp.ToString() })))
                    .Select(y => y.h)
        });

任务是为每个公司的 id 构建 id 的“金字塔”：121for 3、12321for4等等（如果有公司的 id 像 1、2、3 4）。给定查询的想法是在 2 个集合中获取所有小于当前的 id，然后将它们连接起来，以降序排列第二个集合（金字塔的顶部重复，但我稍后会回到它）。

问题是该order by子句不是针对每个集合单独执行的，最后我得到了类似于1 2 3 1 2 3id 为 4 的公司的信息。如何以不同的顺序对嵌套查询进行排序？

UPD1：我使用的数据：

桌子db.Companies

ID_comp | name
--------------------
   1    |Don_avia  
   2    |Aeroflot  
   3    |Dale_avia 
   4    |air_France
   5    |British_AW

输出：

1:
2: 1 1
3: 1 2 1 2
4: 1 2 3 1 2 3
5: 1 2 3 4 1 2 3 4

UPD2：结果查询：

SELECT 
[Extent1].[ID_comp] AS [ID_comp], 
[Project3].[C2] AS [C1], 
[Project3].[C1] AS [C2]
FROM  [dbo].[Company] AS [Extent1]
OUTER APPLY  (SELECT 
    [UnionAll1].[C1] AS [C1], 
    1 AS [C2]
    FROM  (SELECT 
         CAST( [Extent2].[ID_comp] AS nvarchar(max)) AS [C1]
        FROM [dbo].[Company] AS [Extent2]
        WHERE [Extent1].[ID_comp] > [Extent2].[ID_comp]
    UNION ALL
        SELECT 
         CAST( [Extent3].[ID_comp] AS nvarchar(max)) AS [C1]
        FROM [dbo].[Company] AS [Extent3]
        WHERE [Extent1].[ID_comp] > [Extent3].[ID_comp]) AS [UnionAll1] ) AS [Project3]
ORDER BY [Extent1].[ID_comp] ASC, [Project3].[C2] ASC
4

2 回答 2

2

看起来您遇到了 EF6 查询翻译错误 - .Concat(SQL UNION ALL) 子查询的排序被忽略。

我发现的解决方法是将虚假限制运算符附加Take(int.MaxValue)到子查询中，这导致 EF6 考虑排序：

hill =
    (from company in db.Companies
     where x.ID_comp > company.ID_comp
     orderby company.ID_comp
     select new { h = company.ID_comp.ToString() }
    ).Take(int.MaxValue)
    .Concat(
    (from company in db.Companies
     where x.ID_comp > company.ID_comp
     orderby company.ID_comp descending
     select new { h = company.ID_comp.ToString() }
    ).Take(int.MaxValue))
    .Select(y => y.h)

生成的 SQL：

SELECT
    [Extent1].[ID_comp] AS [ID_comp],
    [Project5].[C2] AS [C1],
    [Project5].[C1] AS [C2]
    FROM  [dbo].[Company] AS [Extent1]
    OUTER APPLY  (SELECT
        [UnionAll1].[C1] AS [C1],
        1 AS [C2]
        FROM  (SELECT TOP (2147483647)
            [Project1].[C1] AS [C1]
            FROM ( SELECT
                [Extent2].[ID_comp] AS [ID_comp],
                 CAST( [Extent2].[ID_comp] AS nvarchar(max)) AS [C1]
                FROM [dbo].[Company] AS [Extent2]
                WHERE [Extent1].[ID_comp] > [Extent2].[ID_comp]
            )  AS [Project1]
            ORDER BY [Project1].[ID_comp] ASC
        UNION ALL
            SELECT TOP (2147483647)
            [Project3].[C1] AS [C1]
            FROM ( SELECT
                [Extent3].[ID_comp] AS [ID_comp],
                 CAST( [Extent3].[ID_comp] AS nvarchar(max)) AS [C1]
                FROM [dbo].[Company] AS [Extent3]
                WHERE [Extent1].[ID_comp] > [Extent3].[ID_comp]
            )  AS [Project3]
            ORDER BY [Project3].[ID_comp] DESC) AS [UnionAll1] ) AS [Project5]
    ORDER BY [Extent1].[ID_comp] ASC, [Project5].[C2] ASC
于 2019-05-26T14:34:31.027 回答
0 
var comp = db.Companies.Select(x => new
{
    topid = x.ID_comp,
    hill = ((from company in db.Companies.OrderBy(y => y.ID_comp)
        where x.ID_comp > company.ID_comp
        select new { h = company.ID_comp.ToString() })
        .Concat((
        from company in db.Companies.OrderByDescending(y => y.ID_comp)
        where x.ID_comp > company.ID_comp
        select new { h = company.ID_comp.ToString() })))
        .Select(y => y.h)
    });
于 2019-05-26T12:49:03.923 回答