nhibernate joinalias没有建立正确的查询答案

【问题标题】：nhibernate joinalias doesnt build right querynhibernate joinalias没有建立正确的查询
【发布时间】：2013-11-15 23:52:51
【问题描述】：

每当我尝试执行此查询 (QueryOver) 时，我都会收到 SqlException (The multi-part identifier "packageali1_.PackageID" could not be bound.)：

var brandsFromBrandsInManufacturer2 =
  session.QueryOver<Brand>(() => brandAlias)
    .JoinAlias(brand => brand.Package, () => packageAlias)
    .Where(
       brand =>
       brand.ArtificialBrand == 0
     )
    .And(brand => packageAlias.PackageID
       .IsIn(branchPackagesProductGroupShortName.Keys))
    .Select(brand => brand.BrandName,
       brand => packageAlias.PackageID)
    List<object[]>();

我的映射似乎有错误：

public class PackageMap : ClassMap<Package>
{
    public PackageMap()
    {
        Table("Packages");
        Id(x => x.PackageID).GeneratedBy.Identity();
        Map(x => x.Aggregated).CustomType<PackageAggregation>();
        References(x => x.DataEndPeriod, "DataEndPeriodID");
        References(x => x.Country, "CountryID");
        References(x => x.ProductGroup, "ProductGroupID");

        HasMany(x => x.PackageHierarchies).KeyColumns.Add("PackageId");
        HasMany(x => x.Brands).KeyColumns.Add("PackageId").Inverse();
    } 
}


public BrandMap()
    {
        Table("Brands");
        CompositeId().KeyProperty(x =>x.BrandId).KeyReference(x => x.Package, "PackageId");
        Map(x => x.BrandName);
        References(x => x.Manufacturer).Columns(x => x.ManufacturerId).Nullable();
        Map(x => x.ArtificialBrand);
    }

但我找不到问题所在。我发现的唯一事实是，Brand 具有经典 ID 键，但 Package 具有复合键。

PS：来自 nHibernate 的 SQL 查询是：

 SELECT this_.BrandName as y0_, packageali1_.PackageID as y1_ FROM CD.Brands this_ WHERE this_.ArtificialBrand = @p0 and packageali1_.PackageID in (...)

如您所见，没有 JOIN。

谁能指点我哪里出了问题？

【问题讨论】：

标签： c# sql nhibernate fluent-nhibernate

【解决方案1】：

这里的解决方案是直接使用 Key 属性 Package，而不是其别名。因此，让我们直接通过brand.Package.PackageID 导航而不是packageAlias.PackageID。

另外，如果我们创建了这么多别名，让我们使用它们

var brandsFromBrandsInManufacturer2 = session
    .QueryOver<Brand>(() => brandAlias)
    .JoinAlias(() => brandAlias.Package, () => packageAlias) // use brandAlias
    .Where(() => brandAlias.ArtificialBrand == 0 )
    // no go to Package directly, not via packageAlias
    .And(() => brandAlias.Package.PackageID
       .IsIn(branchPackagesProductGroupShortName.Keys))
    // the same here, the brand.Package...
    .Select(brand => brand.BrandName,
       brand => brand.Package.PackageID)
    List<object[]>();

嗯，第二行实际上是多余的。所以它可能是这样的：

var list = session
    .QueryOver<Brand>(() => brandAlias)
    .Where(() => brandAlias.ArtificialBrand == 0 )
    .And(() => brandAlias.Package.PackageID
       .IsIn(branchPackagesProductGroupShortName.Keys))
    .Select(brand => brand.BrandName,
            brand => brand.Package.PackageID)
    List<object[]>();

【讨论】：