分组项目和计数

Question

我的桌子如下

Main_ID | Child_ID | Activity |
1       |1         | Start    
1       |2         | Stop    
1       |3         | Stop    
2       |1         | Start
2       |3         | Stop

我正在寻找的是

Main_ID | Start | Stop
1       |1      |2
2       |1      |1 

因此，在第一列中，我想要水平列出所有Main_Ids和不同的活动。 之后，我想在Main_ID的每个活动下显示不同的Child_Ids的计数。

我试过的是

var result = from q in db.Table
    where q.Child_ID != null
    group 1 by new { q.Main_ID,q.Child_ID, q.Activity } into g
    select new MyList
    {
        Main_ID = g.Key.Main_ID,
        Child_ID = g.Key.Child_ID,
        Activity = g.Key.Activity,
        Count = g.Count()
    }
    into p orderby p.Main_ID,p.Child_ID select p;

但有了这个，我没有得到我所说的。

我使用以下内容实现了Child_ID

var result2 = result.GroupBy(x => x.Child_ID)
    .Select(grp => new MyList2
    {
        Child_ID = grp.Key,
        StartCount = grp.Where(x => x.Activity == "Start")
            .Select(x => x.Count).Cast<Int32>().FirstOrDefault(),
        StopCount = grp.Where(x => x.Activity == "Stop")
            .Select(x => x.Count).Cast<Int32>().FirstOrDefault()
    });

不知道如何针对Main_ID显示它

Answer 1

考虑这个课程：

public class Foo
{
    public int Main_ID {get;set;}
    public int Child_ID {get;set;}
    public string Activity {get;set;}
}

有了这些数据：

var ls=new List<Foo>
    {
        new Foo{Main_ID=1,Child_ID=1,Activity="Start"},
        new Foo{Main_ID=1,Child_ID=2,Activity="Stop"},
        new Foo{Main_ID=1,Child_ID=3,Activity="Stop"},
        new Foo{Main_ID=2,Child_ID=1,Activity="Start"},
        new Foo{Main_ID=2,Child_ID=3,Activity="Stop"},
    };

你可以这样做：

var result = ls
    .GroupBy (g =>g.Main_ID)
    .Select (g =>new 
    {
       Main_ID = g.Key,
       Start = g.Where(s=>s.Actvity == "Start").Select(x => x.Child_ID).Distinct().Count(),
       Stop = g.Where(s=>s.Actvity == "Stop").Select(x => x.Child_ID).Distinct().Count(),
    } 
    ).ToList();

结果：

Main_ID Start Stop
1       1     2 
2       1     1 

Answer 2

所有，

谢谢你的帮助。

我可以使用以下内容

 var v = from q in myTable
                where q.Child_ID != null
                orderby q.ModifiedDate descending
                select q;

        var result2 = v
            .GroupBy(g => new
        {
            g.Main_ID
        })
         .Select(grp => new MyClass
         {
             Main_ID = grp.Key.Main_ID,
             StartCount = grp.Where(x=> x.Activity == "Start").Select(x => x.Child_ID).Distinct().Count(),
             StopCount = grp.Where(x => x.Activity == "Stop").Select(x => x.Child_ID).Distinct().Count()
         });

我正在使用这个获得预期的resuts。

现在; 我想知道这是否是正确的方法，如果两个查询可以合并。

由于它有代码，没有使用评论发布; 对不起:-)