如何对多列进行分组并计数？

Question

Firstly, I just cannot explain my question in the title properly, but I don't think its a duplicate. I have a List of model which id like to group by multiple fields, then count them into new field, and keep all the other field in the result. I am sorry for the bad explanation, I've been researching how to do this for hours and I just cannot figure it out.. I would like to get from this:

SaleID	Name	Product	Address	Phone	PrintType
112	Joe	Apple	New street 12	11223344	PrintType1
112	Joe	Apple	New street 12	11223344	PrintType2
112	Joe	Apple	New street 12	11223344	PrintType2
112	Joe	Apple	New street 12	11223344	PrintType2
112	Joe	Apple	New street 12	11223344	PrintType3
113	Joe	Kiwi	New street 12	11223344	PrintType3
114	Jane	Orange	New street 19	72754722	PrintType1
115	John	Orange	New street 11	99236527	PrintType2
115	John	Orange	New street 11	99236527	PrintType2

Grouped by SaleID and PrintType into Something like this:

SaleID	Name	Product	Address	Phone	NoOfPrintType1	NoOfPrintType2	NoOfPrintType3
112	Joe	Apple	New street 12	11223344	1	3	1
113	Joe	Kiwi	New street 12	11223344	0	0	1
114	Jane	Orange	New street 19	72754722	1	0	0
115	John	Orange	New street 11	99236527	0	2	0

Preferably id like to use LINQ, but id be good with SQL too, id just like to avoid using a for loop if possible. Edit.: There are a set number of printtypes so it wouldn't need to be dynamic.

Answer 1

In order to aggregate the data for a set number of PrintTypes, you can group by SaleId as the additional data like address, phone and product are the same for a SaleId (based on your sample data).

var aggregated = from x in GenerateSales() 
    group x by x.SaleId into g // Assume that SaleId is the key that you want to group by
    select new Aggregate() 
    { 
        SaleId = g.Key, 
        // Additional data that are the same for all rows with the same SaleId
        Name = g.First().Name, 
        Product = g.First().Product, 
        Address = g.First().Address, 
        Phone = g.First().Phone, 
        // Calculate counts of Print Types
        NoOfPrintType1 = g.Where(x => x.PrintType == "PrintType1").Count(),
        NoOfPrintType2 = g.Where(x => x.PrintType == "PrintType2").Count(),
        NoOfPrintType3 = g.Where(x => x.PrintType == "PrintType3").Count(),
    };

The Linq statement first groups by SaleId and then creates an object for each SaleId, that comprises

• the SaleId
• the additional data like address, phone...
• the count for each known PrintType (calculated by filtering the items of the group and then counting the rows)

Below you can find a sample that generates test data and outputs the result.

Result

112 | Joe | Apple | New street 12 | 11223344 | 1 | 3 | 1
113 | Joe | Kiwi | New street 12 | 11223344 | 0 | 0 | 1
114 | Jane | Orange | New street 19 | 72754722 | 1 | 0 | 0
115 | John | Orange | New street 11 | 99236527 | 0 | 2 | 0

Sample code

using System;
using System.Collections.Generic;
using System.Linq;

namespace LinqTest
{
    class Sale 
    {
        public string SaleId { get; set; }
        public string Name { get; set; }
        public string Product { get; set; }
        public string Address { get; set; }
        public string Phone { get; set; }
        public string PrintType { get; set; }
    }

    class Aggregate 
    {
        public string SaleId { get; set; }
        public string Name { get; set; }
        public string Product { get; set; }
        public string Address { get; set; }
        public string Phone { get; set; }
        public int NoOfPrintType1 { get; set; }
        public int NoOfPrintType2 { get; set; }
        public int NoOfPrintType3 { get; set; }

        public override string ToString() 
        {
            return $"{SaleId} | {Name} | {Product} | {Address} | {Phone} | {NoOfPrintType1} | {NoOfPrintType2} | {NoOfPrintType3}";
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var aggregated = from x in GenerateSales() 
                group x by x.SaleId into g // Assume that SaleId is the key that you want to group by
                select new Aggregate() 
                { 
                    SaleId = g.Key, 
                    // Additional data that are the same for all rows with the same SaleId
                    Name = g.First().Name, 
                    Product = g.First().Product, 
                    Address = g.First().Address, 
                    Phone = g.First().Phone, 
                    // Calculate counts of Print Types
                    NoOfPrintType1 = g.Where(x => x.PrintType == "PrintType1").Count(),
                    NoOfPrintType2 = g.Where(x => x.PrintType == "PrintType2").Count(),
                    NoOfPrintType3 = g.Where(x => x.PrintType == "PrintType3").Count(),
                };
            foreach(var a in aggregated)
            {
                Console.WriteLine(a.ToString());
            }
        }

        static IEnumerable<Sale> GenerateSales()
        {
            yield return new Sale() { SaleId = "112", Name = "Joe", Product = "Apple", Address = "New street 12", Phone = "11223344", PrintType = "PrintType1" };
            yield return new Sale() { SaleId = "112", Name = "Joe", Product = "Apple", Address = "New street 12", Phone = "11223344", PrintType = "PrintType2" };
            yield return new Sale() { SaleId = "112", Name = "Joe", Product = "Apple", Address = "New street 12", Phone = "11223344", PrintType = "PrintType2" };
            yield return new Sale() { SaleId = "112", Name = "Joe", Product = "Apple", Address = "New street 12", Phone = "11223344", PrintType = "PrintType2" };
            yield return new Sale() { SaleId = "112", Name = "Joe", Product = "Apple", Address = "New street 12", Phone = "11223344", PrintType = "PrintType3" };
            yield return new Sale() { SaleId = "113", Name = "Joe", Product = "Kiwi", Address = "New street 12", Phone = "11223344", PrintType = "PrintType3" };
            yield return new Sale() { SaleId = "114", Name = "Jane", Product = "Orange", Address = "New street 19", Phone = "72754722", PrintType = "PrintType1" };
            yield return new Sale() { SaleId = "115", Name = "John", Product = "Orange", Address = "New street 11", Phone = "99236527", PrintType = "PrintType2" };
            yield return new Sale() { SaleId = "115", Name = "John", Product = "Orange", Address = "New street 11", Phone = "99236527", PrintType = "PrintType2" };
        }
    }
}

Answer 2

you can use this SQL query

with x as (
   SELECT  [SaleID],[Name],[Product],[Address],[Phone],[PrintType]
          ,case when [PrintType]='PrintType1' then count(*) else 0 end NoOfPrintType1
          ,case when [PrintType]='PrintType2' then count(*) else 0 end NoOfPrintType2
          ,case when [PrintType]='PrintType3' then count(*) else 0 end NoOfPrintType3
      FROM [Table_1]
      group by [SaleID] ,[Name],[Product],[Address],[Phone] ,[PrintType])
    
    select [SaleID],[Name],[Product],[Address],[Phone]
          ,sum(NoOfPrintType1)NoOfPrintType1
          ,sum(NoOfPrintType2)NoOfPrintType2
          ,sum(NoOfPrintType3)NoOfPrintType3 from x
   group by [SaleID]
          ,[Name],[Product],[Address],[Phone]