Question

我的项目中有两个类，如下所示：

public class Teacher
{
    public virtual long Id {get;set;}
    public virtual IList<Student> Students {get;set;}
}


public class Student
{
    public virtual long Id {get;set;}
    public virtual string Name {get;set;}
}

我需要一个查询，通过计数结果获取学生对每个教师和小组的计数。还有每个计数的频率（呃......计数数）。我不知道如何使用queryover执行此操作。就像给出这样的数据一样：

teacher1.Students = [student1,student2,student3] //teacher1's student count is 3
teacher2.Students = [student4]
teacher3.Students = [student5,student6,student7]
teacher4.Students = [student8]
teacher5.Students = [] //empty

我需要这样的查询结果：

[
[0,1], //1 teacher has 0 students
[1,2], 
[3,2] //2 teachers have 3 students
]

更新：sql是这样的：

select tc.tCount, count(tc.TRID)
from (select tr.Id as TRID, count(std.Id) as tCount
from Teacher tr
JOIN Student std on std.TeacherId = tr.Id
GROUP BY tr.Id ) as tc GROUP BY tc.tCount

Answer 1

            MyDTO myDTO = null;
            Student studentAlias = null;
            Teacher teacherAlias = null;
            var results = _session.QueryOver<Teacher>(()=>teacherAlias)
               .JoinAlias(x=>x.Students,()=>studentAlias, JoinType.LeftOuterJoin)
               .SelectList(list => list
                  .SelectGroup(m => m).WithAlias(() => myDTO.Teacher)
                  .SelectCount(m => studentAlias.Id).WithAlias(() => myDTO.Count)
               )
               .TransformUsing(Transformers.AliasToBean<MyDTO>())
               .List<MyDTO>();

DTO：

public class MyDTO{
   public Teacher Teacher {get;set;} //or just name or whatever you need
   public int Count {get;set;}
}

我可以使用Nhibernate QueryOver按集合的实体计数进行分组和计数吗？

1 个答案: