通过公共外键合并 table 个字段

Question

我是sql&linq的新手，一直卡在一个奇怪的问题中：

我有 3 个表，简化后的样子：

+-----------+
|   Order   |
+-----------+
| ID | Name |
+-----------+

+-----------------------+
|       Ticket_01       |
+-----------------------+
| ID | Value | Order_ID |
+-----------------------+

+-----------------------+
|       Ticket_02       |
+-----------------------+
| ID | Value | Order_ID |
+-----------------------+

关系是 1（顺序）对多（Ticket_01）和 1（顺序）对多（Ticket_02）其中每个订单 "may contain"，例如 2 Ticket_01 和 5 Ticket_02.

我有一个 class，其中包含每个订单的数据：

（简体）

public class OrderData
{
     string orderName; 
     decimal tickets_01_ValueSumatorium;
     int numberOfTickets_01_withValueGreaterThan50;
     decimal tickets_02_ValueSumatorium;
}

所以我想按 "Order" 分组，使用 linq，每个 "Ticket_01" 和 "Ticket_02"。

我正在尝试这样的事情：

var list = (from Order in db.Orders
            join Ticket_01 in db.Tickets_01 on Order.ID equals Ticket_01.Order.Id
            join Ticket_02 in db.Tickets_02 on Order.ID equals Ticket_02.Order.Id
            group new {Ticket_01, Ticket_02} by Order into group
            select new OrderData
            {
                orderName = group.Key.Name,
                tickets_01_ValueSumatorium = group.Sum(t => Tickets_01.Value),
                // etc etc (filling each class field)
            }).ToList();

但这样做，结果会重复或三次，或四次，等等。我"understand"原因，但我也认为应该有一种“"easy/fast"”的方式来group/merge 具有公共外键 (Order_ID) 的票据数据。

如果没有awesom/magic的方法，我想知道各位高手认为哪种方法比较好，因为我是一个一个的gettig数据，一个一个的合并通过在我提到的 class 中保存订单 ID，逐个保存：S

谢谢大家！先post这里^^。如果需要任何说明，我会在这里。

Answer 1

db.Orders join db.Tickets_01 join db.Tickets_02部分将给定订单的allTicket_01s与allTicket_02s连接起来，给你 n x m 行，其中 n 是订单的 Ticket_01s 的编号，m 是它的 Ticket_02s 的编号（这也意味着如果订单没有任何一种类型的票证，你将一无所获） .

您似乎想要实现的目标是：每个订单一个结果，并在订单各自的门票集合上汇总。

from order in db.Orders
select new
{
    Order = order,
    Tickets01 = from ticket in db.Tickets_01 where ticket.OrderId == order.ID select ticket,
    Tickets02 = from ticket in db.Tickets_02 where ticket.OrderId == order.ID select ticket
} into orderWithTickets
select new OrderData
{
    orderName = orderWithTickets.Order.Name,
    tickets_01_ValueSumatorium = orderWithTickets.Tickets01.Sum(t => t.Value),
    numberOfTickets_01_withValueGreaterThan50 = (from t in orderWithTickets.Tickets01 where t.Value > 50 select t).Sum(t => t.Value),
    // ...
};

，或等效（我更喜欢因为我不喜欢查询语法）：

db.Orders.Select(order => new
{
    Order = order,
    Tickets01 = db.Tickets_01.Where(ticket => ticket.OrderId == order.ID),
    Tickets02 = db.Tickets_02.Where(ticket => ticket.OrderId == order.ID)
})
.Select(orderWithTickets => new OrderData
{
    orderName = orderWithTickets.Order.Name,
    tickets_01_ValueSumatorium = orderWithTickets.Tickets01.Sum(t => t.Value),
    numberOfTickets_01_withValueGreaterThan50 = orderWithTickets.Tickets01.Where(t => t.Value > 50).Sum(t => t.Value),
    // ...
})

感觉您应该将订单的门票建模为 navigation properties，在这种情况下您只需要：

db.Orders.Select(order => new OrderData
{
    orderName=order.Name,
    tickets_01_ValueSumatorium = order.Tickets_01.Sum(t=>t.Value),
    numberOfTickets_01_withValueGreaterThan50 = order.Tickets_01.Where(t => t.Value > 50).Sum(t => t.Value)
    // ...
});

Answer 2

这是你想做的吗？

List<Order> orders = new List<Order>();
orders.Add(new Order() { Id = 1, Name = "Order1" });
orders.Add(new Order() { Id = 2, Name = "Order2" });
List<Ticket1> ticket1List = new List<Ticket1>();
ticket1List.Add(new Ticket1() { Id = 10, OrderId = 1, Value = 2 });
ticket1List.Add(new Ticket1() { Id = 20, OrderId = 1, Value = 4 });
List<Ticket2> ticket2List = new List<Ticket2>();
ticket2List.Add(new Ticket2() { Id = 100, OrderId = 1, Value = 1 });
ticket2List.Add(new Ticket2() { Id = 200, OrderId = 1, Value = 3 });
ticket2List.Add(new Ticket2() { Id = 300, OrderId = 2, Value = 5 });

var sumT1 = from o in orders
            from t1 in ticket1List.Where(a => a.OrderId == o.Id).GroupBy(a => a.OrderId)
            select new { OrderId = o.Id, SumT1 = t1.Sum(a => a.Value) };

var sumT2 = from o in orders
            from t2 in ticket2List.Where(a => a.OrderId == o.Id).GroupBy(a => a.OrderId)
            select new { OrderId = o.Id, SumT2 = t2.Sum(a => a.Value) };

var list = from o in orders
           from s1 in sumT1.Where(x => x.OrderId == o.Id).DefaultIfEmpty()
           from s2 in sumT2.Where(x => x.OrderId == o.Id).DefaultIfEmpty()
           select new OrderData()
           {
               OrderName = o.Name,
               Ticket1Sum = s1?.SumT1 ?? 0,
               Ticket2Sum = s2?.SumT2 ?? 0             
           };

类:

class OrderData
{
    public string OrderName { get; set; }
    public int Ticket1Sum { get; set; }
    public int Ticket2Sum { get; set; }
}

class Order
{
    public int Id { get; set; }
    public string Name { get; set; }
}

class Ticket1
{
    public int Id { get; set; }
    public int Value { get; set; }
    public int OrderId { get; set; }
}

class Ticket2
{
    public int Id { get; set; }
    public int Value { get; set; }
    public int OrderId { get; set; }
}

通过公共外键合并 table 个字段

Merging table fields by common foreign key

c#

sql

linq

asp.net-mvc

entity