Question

我想使用条件重现以下查询：

select a.ID as article, count(c.ID) as commentsCount
from Comments c 
left outer join Articles a on a.ID=c.ArticleID 
where a.ID in (2,10)
group by a.ID

我写了它，但在某处我必须有错误，因为结果与我预期的不同。

标准：

ICriteria criteria = Session.CreateCriteria<Comment>("c")  
                .CreateCriteria("Article", "a", 
                                NHibernate.SqlCommand.JoinType.LeftOuterJoin)
                .Add(Restrictions.In("a.ID", articleIDs))
                .SetProjection(Projections.Property("a.ID"))
                .SetProjection(Projections.Count("c.ID"))
                .SetProjection(Projections.GroupProperty("a.ID"));

NHibernate使用以下标准生成以下sql：

SELECT   a1_.ID as y0_
FROM     Comments this_
         left outer join Articles a1_
           on this_.ArticleID = a1_.ID
WHERE    a1_.ID in (2 /* @p0 */,10 /* @p1 */)
GROUP BY a1_.ID

映射：

public class Comment : EntityBase<int>
{
        public virtual Article Article { set; get; }

}

public CommentMap()
        {
            Id(x => x.ID).GeneratedBy.Identity();        
            References(x => x.Article).Not.Nullable()
                                      .LazyLoad().Cascade
                                      .SaveUpdate().Column("ArticleID");
        }

Answer 1

每次使用SetProjection时，都会替换上一个。

您需要使用：

.SetProjection(Projections.Property("a.ID"),
               Projections.Count("c.ID"),
               Projections.GroupProperty("a.ID"))

使用nhibernate中的条件创建查询的问题

1 个答案: