EF代码首先创建废弃列

我有以下用于数据库的类：

public abstract class BaseProduct
{
    public int ID { get; set; }
    [Required, StringLength(100), Display(Name = "Name")]
    public string ProductName { get; set; }
    [Required, StringLength(10000), Display(Name = "Product Description"), DataType(DataType.MultilineText)]
    public string Description { get; set; }
    public string ImagePath { get; set; }
    [Display(Name = "Price")]
    public double? UnitPrice { get; set; }
    public int? CategoryID { get; set; }
    public virtual Category Category { get; set; }
    public string Author { get; set; }
    public virtual ICollection<PriceRelation> Prices { get; set; }
}
[Table("Packages")]
public class Package : BaseProduct
{
    public virtual ICollection<Product> Products { get; set; }
}
[Table("Products")]
public class Product : BaseProduct
{
    public virtual ICollection<Package> Packages { get; set; }
}
public class Category
{
    [ScaffoldColumn(false)]
    public int CategoryId { get; set; }
    [Required, StringLength(100), Display(Name = "Name")]
    public string CategoryName { get; set; }
    [Display(Name = "Category Description")]
    public string Description { get; set; }
    public int? ParentID { get; set; }
    [ForeignKey("ParentID")]
    public virtual Category Parent { get; set; }
    public virtual ICollection<Category> Children { get; set; } 
    public virtual ICollection<Product> Products { get; set; }
}

这就是模型构建者：

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Package>().HasMany(p => p.Products).WithMany(p => p.Packages)
            .Map(m =>
                {
                    m.ToTable("PackageRelations");
                    m.MapLeftKey("PackageID");
                    m.MapRightKey("ProductID");
                });
    }
    }

它以以下方式建立了我想要的关系：

表：基本产品列：ID，ProductName，描述，ImagePath，单价，类别ID，作者

表：程序包列：ID

表：产品列：ID，Category_CategoryID

我想知道的是，它为什么在products表中创建列Category_CategoryID？当我填充表时，这一列中的所有值都是null，所以看起来它没有被用于任何事情。

此外，它似乎没有正确的关系，因为该类别上的虚拟产品集合总是空的。