Question

我得到了一个包含3个一对多关系的表（一对多对多关系以及与额外数据的第三对多关系），但我想从多对多关系的一方支撑一些关系。我不希望它与多对多关系的另一方联系在一起，所以我想把它变成可空的但我（没有惊喜）不能这样做，因为它是一个主键为了它。但是，有多种解决方法可以为多对多关系中的一方获取null吗？

这是SQL源代码：

    CREATE TABLE [dbo].[ConnectionPointRoutes] (
[ConnectionPointId] INT NOT NULL,
[RouteId]           INT NOT NULL,
[SegmentId]         INT NOT NULL,
[Position]          INT NOT NULL,
CONSTRAINT [PK_dbo.ConnectionPointRoutes] PRIMARY KEY CLUSTERED ([ConnectionPointId] ASC, [RouteId] ASC, [SegmentId] ASC),
CONSTRAINT [FK_dbo.ConnectionPointRoutes_dbo.ConnectionPoints_ConnectionPointId] FOREIGN KEY ([ConnectionPointId]) REFERENCES [dbo].[ConnectionPoints] ([ConnectionPointId]) ON DELETE CASCADE,
CONSTRAINT [FK_dbo.ConnectionPointRoutes_dbo.Routes_RouteId] FOREIGN KEY ([RouteId]) REFERENCES [dbo].[Routes] ([RouteId]) ON DELETE CASCADE,
CONSTRAINT [FK_dbo.ConnectionPointRoutes_dbo.Segments_SegmentId] FOREIGN KEY ([SegmentId]) REFERENCES [dbo].[Segments] ([SegmentId]) ON DELETE CASCADE
);
GO
CREATE NONCLUSTERED INDEX [IX_ConnectionPointId]
    ON [dbo].[ConnectionPointRoutes]([ConnectionPointId] ASC);
GO
CREATE NONCLUSTERED INDEX [IX_RouteId]
    ON [dbo].[ConnectionPointRoutes]([RouteId] ASC);
GO
CREATE NONCLUSTERED INDEX [IX_SegmentId]
    ON [dbo].[ConnectionPointRoutes]([SegmentId] ASC);

这是模型，注意我让它可以为空但数据库仍然把它作为一个不可为空的项目

namespace InBuildingNavigator.Data.Models
{
    public class ConnectionPointRoute
    {
        public int ConnectionPointId { get; set; }
        public int? RouteId { get; set; }
        public int? SegmentId { get; set; }
        public  int Position { get; set; }
        public ConnectionPoint ConnectionPoint { get; set; }
        public Route Route { get; set; }
        public Segment Segment { get; set; }
    }
}

对此问题的解决方法有任何想法吗？

Answer 1

问题在这里得到解决：Optional One to many relationship

connectionpointroute modelbuilder必须是这样的：

modelBuilder.Entity<ConnectionPointRoute>()
    .HasKey(c => new {c.ConnectionPointId, c.RouteId});

与可空密钥

1 个答案: