Apply Group by on latest group

Question

Please consider this table:

Organization           State          Year          Month        Value
----------------------------------------------------------------------
   O1                   NY             2017          1            1
   01                   WA             2017          1            2
   01                   SA             2017          1            3
   O1                   NY             2017          2            4
   01                   WA             2017          2            5
   01                   SA             2017          2            6
   O2                   NY             2015          9            7
   02                   WA             2015          9            8
   02                   SA             2015          9            9
   O2                   NY             2016          1            10
   02                   WA             2016          1            11
   02                   SA             2016          1            12
   O3                   NY             2017          8            13
   03                   WA             2017          8            14
   03                   SA             2017          8            15

I want to create this result:

Organization           Year          Month        Sum
------------------------------------------------------
    01                 2017            2           15
    02                 2016            1           33
    03                 2017            8           42

I want to group on latest Year, Month and calculate sum. In above sample Organization 01 has data for 2 periods but I want to group on latest period.

---

UPDATE 1)

var query = from o in MyList
            group o by new {c.Organization, c.Year , c.Month} int grp
            select new 
            { 
                grp.Key.Organization, 
                grp.Key.Year, 
                grp.Key.Month, 
                grp.Sum() 
            };

Answer 1

Try below query:

class Program
{
    static void Main(string[] args)
    {           

        var results = (from o in MyList
                       group o by new { o.Organization } into g
                       select new
                       {
                           Org_Id = g.Key.Organization,
                           Year = g.Select(x => x.Year)
                                   .Max(),
                           Month = g.Where(x => x.Year == g.Select(y => y.Year).Max())
                                    .Select(z => z.Month)
                                    .Max(),
                           Sum = g.Where(x => x.Month == g.Where(y => y.Year == g.Select(z => z.Year).Max())
                                                          .Select(y => y.Month)
                                                          .Max())
                                  .Select(z => z.Value)
                                  .Sum()
                       }).ToList();

        results.ForEach(x => Console.WriteLine($"Org_Id: {x.Org_Id} \t Year: {x.Year} \t Month: {x.Month} \t Sum: {x.Sum}"));

        Console.ReadLine();
    }
}

What we done in query:

1) Group by Organization

2) Org_Id: as key of your group

3) Year: select Max year from group.

4) Month: select Max of month by selecting Max of year from group.

5) Sum: sum of value by selecting Max of month of Max of year from group.

Output:

Sql for above query:

SELECT [t1].[Organization] AS [Org_Id], (
    SELECT MAX([t2].[Year])
    FROM [Org] AS [t2]
    WHERE (([t1].[Organization] IS NULL) AND ([t2].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t2].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t2].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t2].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t2].[Organization]))))
    ) AS [Year], (
    SELECT MAX([t3].[Month])
    FROM [Org] AS [t3]
    WHERE ([t3].[Year] = ((
        SELECT MAX([t4].[Year])
        FROM [Org] AS [t4]
        WHERE (([t1].[Organization] IS NULL) AND ([t4].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t4].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t4].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t4].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t4].[Organization]))))
        ))) AND ((([t1].[Organization] IS NULL) AND ([t3].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t3].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t3].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t3].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t3].[Organization])))))
    ) AS [Month], (
    SELECT SUM([t5].[Value])
    FROM [Org] AS [t5]
    WHERE ([t5].[Month] = ((
        SELECT MAX([t6].[Month])
        FROM [Org] AS [t6]
        WHERE ([t6].[Year] = ((
            SELECT MAX([t7].[Year])
            FROM [Org] AS [t7]
            WHERE (([t1].[Organization] IS NULL) AND ([t7].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t7].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t7].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t7].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t7].[Organization]))))
            ))) AND ((([t1].[Organization] IS NULL) AND ([t6].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t6].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t6].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t6].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t6].[Organization])))))
        ))) AND ((([t1].[Organization] IS NULL) AND ([t5].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t5].[Organization] IS NOT NULL) AND ((([t1].[Organization] IS NULL) AND ([t5].[Organization] IS NULL)) OR (([t1].[Organization] IS NOT NULL) AND ([t5].[Organization] IS NOT NULL) AND ([t1].[Organization] = [t5].[Organization])))))
    ) AS [Sum]
FROM (
    SELECT [t0].[Organization]
    FROM [Org] AS [t0]
    GROUP BY [t0].[Organization]
    ) AS [t1]

Output:

Answer 2

I think your logic to get the output is wrong. What I can see from the Output grouping is done in 2 steps

Step1

Group By Organization, State, MAX(Year) AS Year, MAX(Month) AS Month, MAX(Value) As Value

Step2

Group By Organization, MAX(Year) AS Year, MAX(Month) AS Month, SUM(Value) As Value

Final Output has the sum of max Values under each State for an Organization.

If my assumption is correct, then you will be able to write the LINQ query for that