是否可以使用LINQ透视数据?
我想知道是否可以使用LINQ从以下布局透视数据:是否可以使用LINQ透视数据?,linq,pivot-table,Linq,Pivot Table,我想知道是否可以使用LINQ从以下布局透视数据: CustID | OrderDate | Qty 1 | 1/1/2008 | 100 2 | 1/2/2008 | 200 1 | 2/2/2008 | 350 2 | 2/28/2008 | 221 1 | 3/12/2008 | 250 2 | 3/15/2008 | 2150 变成这样: CustID | Jan- 2008 | Feb- 2008 | Mar - 20
CustID | OrderDate | Qty
1 | 1/1/2008 | 100
2 | 1/2/2008 | 200
1 | 2/2/2008 | 350
2 | 2/28/2008 | 221
1 | 3/12/2008 | 250
2 | 3/15/2008 | 2150
变成这样:
CustID | Jan- 2008 | Feb- 2008 | Mar - 2008 |
1 | 100 | 350 | 250
2 | 200 | 221 | 2150
将您的数据按月份分组,然后将其投影到一个新的datatable中,其中包含每个月的列。新表将是您的数据透视表。类似的内容
List<CustData> myList = GetCustData();
var query = myList
.GroupBy(c => c.CustId)
.Select(g => new {
CustId = g.Key,
Jan = g.Where(c => c.OrderDate.Month == 1).Sum(c => c.Qty),
Feb = g.Where(c => c.OrderDate.Month == 2).Sum(c => c.Qty),
March = g.Where(c => c.OrderDate.Month == 3).Sum(c => c.Qty)
});
List myList=GetCustData();
var query=myList
.GroupBy(c=>c.CustId)
.选择(g=>new{
CustId=g.Key,
Jan=g.Where(c=>c.OrderDate.Month==1)。Sum(c=>c.Qty),
Feb=g.Where(c=>c.OrderDate.Month==2.Sum(c=>c.Qty),
三月=g.Where(c=>c.OrderDate.Month==3)。总和(c=>c.Qty)
});
Linq中的GroupBy与SQL的工作原理不同。在SQL中,您可以获得键和聚合(行/列形状)。在Linq中,可以将键和任何元素作为键的子元素(层次形状)。若要透视,必须将层次结构投影回您选择的行/列形式。我使用linq扩展方法回答:
// order s(ource) by OrderDate to have proper column ordering
var r = s.Pivot3(e => e.custID, e => e.OrderDate.ToString("MMM-yyyy")
, lst => lst.Sum(e => e.Qty));
// order r(esult) by CustID
(+)通用实现(-)绝对比艾米B的慢
是否有人可以改进我的实现(即该方法对列和行进行排序)?以下是一种更通用的方法,可以使用LINQ透视数据:
IEnumerable<CustData> s;
var groupedData = s.ToLookup(
k => new ValueKey(
k.CustID, // 1st dimension
String.Format("{0}-{1}", k.OrderDate.Month, k.OrderDate.Year // 2nd dimension
) ) );
var rowKeys = groupedData.Select(g => (int)g.Key.DimKeys[0]).Distinct().OrderBy(k=>k);
var columnKeys = groupedData.Select(g => (string)g.Key.DimKeys[1]).Distinct().OrderBy(k=>k);
foreach (var row in rowKeys) {
Console.Write("CustID {0}: ", row);
foreach (var column in columnKeys) {
Console.Write("{0:####} ", groupedData[new ValueKey(row,column)].Sum(r=>r.Qty) );
}
Console.WriteLine();
}
我认为,最简洁的方法是使用查找:
var query =
from c in myList
group c by c.CustId into gcs
let lookup = gcs.ToLookup(y => y.OrderDate.Month, y => y.Qty)
select new
{
CustId = gcs.Key,
Jan = lookup[1].Sum(),
Feb = lookup[2].Sum(),
Mar = lookup[3].Sum(),
};
这是最有效的方法: 检查以下方法。而不是在每个月的每次客户组中迭代
var query = myList
.GroupBy(c => c.CustId)
.Select(g => {
var results = new CustomerStatistics();
foreach (var customer in g)
{
switch (customer.OrderDate.Month)
{
case 1:
results.Jan += customer.Qty;
break;
case 2:
results.Feb += customer.Qty;
break;
case 3:
results.March += customer.Qty;
break;
default:
break;
}
}
return new
{
CustId = g.Key,
results.Jan,
results.Feb,
results.March
};
});
或者这个:
var query = myList
.GroupBy(c => c.CustId)
.Select(g => {
var results = g.Aggregate(new CustomerStatistics(), (result, customer) => result.Accumulate(customer), customerStatistics => customerStatistics.Compute());
return new
{
CustId = g.Key,
results.Jan,
results.Feb,
results.March
};
});
完整解决方案:
using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp
{
internal class Program
{
private static void Main(string[] args)
{
IEnumerable<CustData> myList = GetCustData().Take(100);
var query = myList
.GroupBy(c => c.CustId)
.Select(g =>
{
CustomerStatistics results = g.Aggregate(new CustomerStatistics(), (result, customer) => result.Accumulate(customer), customerStatistics => customerStatistics.Compute());
return new
{
CustId = g.Key,
results.Jan,
results.Feb,
results.March
};
});
Console.ReadKey();
}
private static IEnumerable<CustData> GetCustData()
{
Random random = new Random();
int custId = 0;
while (true)
{
custId++;
yield return new CustData { CustId = custId, OrderDate = new DateTime(2018, random.Next(1, 4), 1), Qty = random.Next(1, 50) };
}
}
}
public class CustData
{
public int CustId { get; set; }
public DateTime OrderDate { get; set; }
public int Qty { get; set; }
}
public class CustomerStatistics
{
public int Jan { get; set; }
public int Feb { get; set; }
public int March { get; set; }
internal CustomerStatistics Accumulate(CustData customer)
{
switch (customer.OrderDate.Month)
{
case 1:
Jan += customer.Qty;
break;
case 2:
Feb += customer.Qty;
break;
case 3:
March += customer.Qty;
break;
default:
break;
}
return this;
}
public CustomerStatistics Compute()
{
return this;
}
}
}
使用系统;
使用System.Collections.Generic;
使用System.Linq;
名称空间控制台
{
内部课程计划
{
私有静态void Main(字符串[]args)
{
IEnumerable myList=GetCustData().Take(100);
var query=myList
.GroupBy(c=>c.CustId)
.选择(g=>
{
CustomerStatistics结果=g.Aggregate(新CustomerStatistics(),(结果,客户)=>result.acculate(客户),CustomerStatistics=>CustomerStatistics.Compute());
还新
{
CustId=g.Key,
结果:1月,
结果:2月,
结果,三月
};
});
Console.ReadKey();
}
私有静态IEnumerable GetCustData()
{
随机=新随机();
int custId=0;
while(true)
{
custId++;
收益返回新的CustData{CustId=CustId,OrderDate=newdatetime(2018,random.Next(1,4),1),Qty=random.Next(1,50)};
}
}
}
公共类数据
{
public int CustId{get;set;}
public DateTime OrderDate{get;set;}
公共整数数量{get;set;}
}
公共类客户统计
{
公共整数Jan{get;set;}
公共int Feb{get;set;}
公共整数{get;set;}
内部客户统计累积(客户数据)
{
开关(customer.OrderDate.Month)
{
案例1:
一月+=客户数量;
打破
案例2:
二月+=客户数量;
打破
案例3:
三月+=客户数量;
打破
违约:
打破
}
归还这个;
}
公共客户统计计算()
{
归还这个;
}
}
}
我无法想象这将如何工作,但我很好奇,请求您包含一些示例代码。在应用透视之前,列表必须是IEnumerable吗?或者也可以在EF的IQueryable上执行此操作(而不必在内存中具体化列表)?@RobVermeulen我可以将该查询转换为sql,因此我希望EF也能够将其转换。试试吧,我想?我测试过了,有点效果。尽管SQLProfiler显示EF不会将其转换为(快速)透视查询,而是转换为几个较慢的子查询。
var query = myList
.GroupBy(c => c.CustId)
.Select(g => {
var results = g.Aggregate(new CustomerStatistics(), (result, customer) => result.Accumulate(customer), customerStatistics => customerStatistics.Compute());
return new
{
CustId = g.Key,
results.Jan,
results.Feb,
results.March
};
});
using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp
{
internal class Program
{
private static void Main(string[] args)
{
IEnumerable<CustData> myList = GetCustData().Take(100);
var query = myList
.GroupBy(c => c.CustId)
.Select(g =>
{
CustomerStatistics results = g.Aggregate(new CustomerStatistics(), (result, customer) => result.Accumulate(customer), customerStatistics => customerStatistics.Compute());
return new
{
CustId = g.Key,
results.Jan,
results.Feb,
results.March
};
});
Console.ReadKey();
}
private static IEnumerable<CustData> GetCustData()
{
Random random = new Random();
int custId = 0;
while (true)
{
custId++;
yield return new CustData { CustId = custId, OrderDate = new DateTime(2018, random.Next(1, 4), 1), Qty = random.Next(1, 50) };
}
}
}
public class CustData
{
public int CustId { get; set; }
public DateTime OrderDate { get; set; }
public int Qty { get; set; }
}
public class CustomerStatistics
{
public int Jan { get; set; }
public int Feb { get; set; }
public int March { get; set; }
internal CustomerStatistics Accumulate(CustData customer)
{
switch (customer.OrderDate.Month)
{
case 1:
Jan += customer.Qty;
break;
case 2:
Feb += customer.Qty;
break;
case 3:
March += customer.Qty;
break;
default:
break;
}
return this;
}
public CustomerStatistics Compute()
{
return this;
}
}
}