nHibernate将属性映射到行的存在

我有以下实体和Fluent NHibernate映射:

public class Advertiser
{
    public virtual int AdvertiserId { get; set; }
    public virtual string AdvertiserName { get; set; }
    public virtual bool IsPriorityEntity { get; set; }
}

public class AdvertiserMapping : ClassMap<Advertiser>
{
    public AdvertiserMapping()
    {
        Id(a => a.AdvertiserId).GeneratedBy.Identity();
        Map(a => a.AdvertiserName);
    }
}

ISpriorityEntity属性通过PriorityEntity表中的行存储在数据库中。
查询如下所示:

Select 
  AdvertiserId, 
  AdvertiserName,  
  CASE WHEN pe.PriorityEntityID IS NOT NULL 
       THEN 1 
       ELSE 0 END as IsPriorityEntity  
From Advertisers adv  
  Left Join PriorityEntity pe 
    on pe.PriorityEntityID = adv.AdvertiserID 
      and pe.EntityTypeID = 6

我不知道如何绘制这样的地图。