Voorbeelden van op methoden gebaseerde querysyntaxis: Join-operators
De voorbeelden in dit onderwerp laten zien hoe u de Join en GroupJoin methoden kunt gebruiken om query's uit te voeren op het AdventureWorks Sales Model met behulp van op methoden gebaseerde querysyntaxis. Het AdventureWorks Sales Model dat in deze voorbeelden wordt gebruikt, is gebaseerd op de tabellen Contact, Adres, Product, SalesOrderHeader en SalesOrderDetail in de voorbeelddatabase AdventureWorks.
In de voorbeelden in dit onderwerp worden de volgende using/Imports instructies gebruikt:
using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using System.Globalization;
using System.Data.EntityClient;
using System.Data.SqlClient;
using System.Data.Common;
Option Explicit On
Option Strict On
Imports System.Data.Objects
Imports System.Globalization
GroupJoin
Opmerking
In het volgende voorbeeld worden de GroupJoin tabellen SalesOrderHeader en SalesOrderDetail uitgevoerd om het aantal orders per klant te vinden. Een groepsdeelname is het equivalent van een left outer join, die elk element van de eerste (linker) gegevensbron retourneert, zelfs als er geen gecorreleerde elementen zich in de andere gegevensbron bevinden.
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
ObjectSet<SalesOrderDetail> details = context.SalesOrderDetails;
var query = orders.GroupJoin(details,
order => order.SalesOrderID,
detail => detail.SalesOrderID,
(order, orderGroup) => new
{
CustomerID = order.SalesOrderID,
OrderCount = orderGroup.Count()
});
foreach (var order in query)
{
Console.WriteLine("CustomerID: {0} Orders Count: {1}",
order.CustomerID,
order.OrderCount);
}
}
Using context As New AdventureWorksEntities
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim details As ObjectSet(Of SalesOrderDetail) = context.SalesOrderDetails
Dim query = orders.GroupJoin(details, _
Function(order) order.SalesOrderID, _
Function(detail) detail.SalesOrderID, _
Function(order, orderGroup) New With _
{ _
.CustomerID = order.SalesOrderID, _
.OrderCount = orderGroup.Count() _
})
For Each order In query
Console.WriteLine("CustomerID: {0} Orders Count: {1}", _
order.CustomerID, order.OrderCount)
Next
End Using
Opmerking
In het volgende voorbeeld worden de tabellen Contact en SalesOrderHeader uitgevoerd GroupJoin om het aantal orders per contactpersoon te vinden. Het aantal orders en id's voor elke contactpersoon wordt weergegeven.
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Contact> contacts = context.Contacts;
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
var query = contacts.GroupJoin(orders,
contact => contact.ContactID,
order => order.Contact.ContactID,
(contact, contactGroup) => new
{
ContactID = contact.ContactID,
OrderCount = contactGroup.Count(),
Orders = contactGroup
});
foreach (var group in query)
{
Console.WriteLine("ContactID: {0}", group.ContactID);
Console.WriteLine("Order count: {0}", group.OrderCount);
foreach (var orderInfo in group.Orders)
{
Console.WriteLine(" Sale ID: {0}", orderInfo.SalesOrderID);
}
Console.WriteLine("");
}
}
Using context As New AdventureWorksEntities
Dim contacts As ObjectSet(Of Contact) = context.Contacts
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim query = contacts.GroupJoin(orders, _
Function(contact) contact.ContactID, _
Function(order) order.Contact.ContactID, _
Function(contact, contactGroup) New With _
{ _
.ContactID = contact.ContactID, _
.OrderCount = contactGroup.Count(), _
.orders = contactGroup.Select(Function(order) order) _
})
For Each group In query
Console.WriteLine("ContactID: {0}", group.ContactID)
Console.WriteLine("Order count: {0}", group.OrderCount)
For Each orderInfo In group.orders
Console.WriteLine(" Sale ID: {0}", orderInfo.SalesOrderID)
Next
Console.WriteLine("")
Next
End Using
Deelnemen
Opmerking
In het volgende voorbeeld wordt een join uitgevoerd via de tabellen Contact en SalesOrderHeader.
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Contact> contacts = context.Contacts;
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
var query =
contacts.Join(
orders,
order => order.ContactID,
contact => contact.Contact.ContactID,
(contact, order) => new
{
ContactID = contact.ContactID,
SalesOrderID = order.SalesOrderID,
FirstName = contact.FirstName,
Lastname = contact.LastName,
TotalDue = order.TotalDue
});
foreach (var contact_order in query)
{
Console.WriteLine("ContactID: {0} "
+ "SalesOrderID: {1} "
+ "FirstName: {2} "
+ "Lastname: {3} "
+ "TotalDue: {4}",
contact_order.ContactID,
contact_order.SalesOrderID,
contact_order.FirstName,
contact_order.Lastname,
contact_order.TotalDue);
}
}
Using context As New AdventureWorksEntities
Dim contacts As ObjectSet(Of Contact) = context.Contacts
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim query = _
contacts.Join( _
orders, _
Function(ord) ord.ContactID, _
Function(cont) cont.Contact.ContactID, _
Function(cont, ord) New With _
{ _
.ContactID = cont.ContactID, _
.SalesOrderID = ord.SalesOrderID, _
.FirstName = cont.FirstName, _
.Lastname = cont.LastName, _
.TotalDue = ord.TotalDue _
})
For Each contact_order In query
Console.WriteLine("ContactID: {0} " _
& "SalesOrderID: {1} " & "FirstName: {2} " _
& "Lastname: {3} " & "TotalDue: {4}", _
contact_order.ContactID, _
contact_order.SalesOrderID, _
contact_order.FirstName, _
contact_order.Lastname, _
contact_order.TotalDue)
Next
End Using
Opmerking
In het volgende voorbeeld wordt een join uitgevoerd via de tabellen Contact en SalesOrderHeader, waarbij de resultaten worden gegroepeerd op contactpersoon-id.
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Contact> contacts = context.Contacts;
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
var query = contacts.Join(
orders,
order => order.ContactID,
contact => contact.Contact.ContactID,
(contact, order) => new
{
ContactID = contact.ContactID,
SalesOrderID = order.SalesOrderID,
FirstName = contact.FirstName,
Lastname = contact.LastName,
TotalDue = order.TotalDue
})
.GroupBy(record => record.ContactID);
foreach (var group in query)
{
foreach (var contact_order in group)
{
Console.WriteLine("ContactID: {0} "
+ "SalesOrderID: {1} "
+ "FirstName: {2} "
+ "Lastname: {3} "
+ "TotalDue: {4}",
contact_order.ContactID,
contact_order.SalesOrderID,
contact_order.FirstName,
contact_order.Lastname,
contact_order.TotalDue);
}
}
}
Using context As New AdventureWorksEntities
Dim contacts As ObjectSet(Of Contact) = context.Contacts
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim query = _
contacts.Join( _
orders, _
Function(ord) ord.ContactID, _
Function(cont) cont.Contact.ContactID, _
Function(cont, ord) New With _
{ _
.ContactID = cont.ContactID, _
.SalesOrderID = ord.SalesOrderID, _
.FirstName = cont.FirstName, _
.Lastname = cont.LastName, _
.TotalDue = ord.TotalDue _
}) _
.GroupBy(Function(record) record.ContactID)
For Each group In query
For Each contact_order In group
Console.WriteLine("ContactID: {0} " _
& "SalesOrderID: {1} " & "FirstName: {2} " _
& "Lastname: {3} " & "TotalDue: {4}", _
contact_order.ContactID, _
contact_order.SalesOrderID, _
contact_order.FirstName, _
contact_order.Lastname, _
contact_order.TotalDue)
Next
Next
End Using