Apex - DML

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本章将讨论如何在Salesforce中执行不同的数据库修改功能。有两种方法可以执行这些功能。

DML语句

DML是在执行插入、更新、删除、Upsert、恢复记录、合并记录或转换潜在客户操作时执行的操作。

DML是Apex中最重要的部分之一，因为几乎每个业务案例都涉及到数据库的更改和修改。

数据库方法

可以使用DML语句执行的所有操作也可以使用数据库方法执行。数据库方法是可以用来执行DML操作的系统方法。与DML语句相比，数据库方法提供了更大的灵活性。

本章将介绍使用DML语句的第一种方法。我们将在后续章节中介绍数据库方法。

DML语句

现在让我们再次考虑化学供应商公司的实例。我们的发票记录的字段包括状态、已付金额、剩余金额、下次付款日期和发票编号。今天创建且状态为“待处理”的发票应更新为“已支付”。

插入操作

插入操作用于在数据库中创建新记录。可以使用Insert DML语句创建任何标准对象或自定义对象的记录。

示例

随着每天为新的客户订单生成新的发票，我们可以在APEX_Invoice__c对象中创建新记录。我们将首先创建一个客户记录，然后可以为该新的客户记录创建一个发票记录。

// fetch the invoices created today, Note, you must have at least one invoice 
// created today

List<apex_invoice__c> invoiceList = [SELECT id, Name, APEX_Status__c,
   createdDate FROM APEX_Invoice__c WHERE createdDate = today];

// create List to hold the updated invoice records
List<apex_invoice__c> updatedInvoiceList = new List<apex_invoice__c>();
APEX_Customer__c objCust = new APEX_Customer__C();
objCust.Name = 'Test ABC';

//DML for Inserting the new Customer Records
insert objCust;
for (APEX_Invoice__c objInvoice: invoiceList) {
   if (objInvoice.APEX_Status__c == 'Pending') {
      objInvoice.APEX_Status__c = 'Paid';
      updatedInvoiceList.add(objInvoice);
   }
}

// DML Statement to update the invoice status
update updatedInvoiceList;

// Prints the value of updated invoices
System.debug('List has been updated and updated values are' + updatedInvoiceList);

// Inserting the New Records using insert DML statement
APEX_Invoice__c objNewInvoice = new APEX_Invoice__c();
objNewInvoice.APEX_Status__c = 'Pending';
objNewInvoice.APEX_Amount_Paid__c = 1000;
objNewInvoice.APEX_Customer__c = objCust.id;

// DML which is creating the new Invoice record which will be linked with newly
// created Customer record
insert objNewInvoice;
System.debug('New Invoice Id is '+objNewInvoice.id+' and the Invoice Number is'
   + objNewInvoice.Name);

更新操作

更新操作用于对现有记录执行更新。在此示例中，我们将把现有发票记录的状态字段更新为“已支付”。

示例

// Update Statement Example for updating the invoice status. You have to create
and Invoice records before executing this code. This program is updating the
record which is at index 0th position of the List.

// First, fetch the invoice created today
List<apex_invoice__c> invoiceList = [SELECT id, Name, APEX_Status__c,
createdDate FROM APEX_Invoice__c];
List<apex_invoice__c> updatedInvoiceList = new List<apex_invoice__c>();

// Update the first record in the List
invoiceList[0].APEX_Status__c = 'Pending';
updatedInvoiceList.add(invoiceList[0]);

// DML Statement to update the invoice status
update updatedInvoiceList;

// Prints the value of updated invoices
System.debug('List has been updated and updated values of records are' 
   + updatedInvoiceList[0]);

Upsert操作

Upsert操作用于执行更新操作，如果要更新的记录不存在于数据库中，则也创建新记录。

示例

假设需要更新客户对象中的客户记录。如果现有客户记录已存在，我们将更新它，否则创建一个新的。这将基于字段APEX_External_Id__c的值。此字段将是我们用来识别记录是否已存在的字段。

注意 − 在执行此代码之前，请在客户对象中创建一个外部ID字段值为“12341”的记录，然后执行以下代码 −

// Example for upserting the Customer records
List<apex_customer__c> CustomerList = new List<apex_customer__c>();
for (Integer i = 0; i < 10; i++) {
   apex_customer__c objcust=new apex_customer__c(name = 'Test' +i,
   apex_external_id__c='1234' +i);
   customerlist.add(objcust);
} //Upserting the Customer Records

upsert CustomerList;

System.debug('Code iterated for 10 times and created 9 records as one record with 
   External Id 12341 is already present');

for (APEX_Customer_c objCustomer: CustomerList) {
   if (objCustomer.APEX_External_Id_c == '12341') {
      system.debug('The Record which is already present is '+objCustomer);
   }
}

删除操作

可以使用Delete DML执行删除操作。

示例

在本例中，我们将删除为测试目的创建的发票，即名称为“测试”的发票。

您也可以在不创建类的情况下从开发人员控制台执行此代码段。

// fetch the invoice created today
List<apex_invoice__c> invoiceList = [SELECT id, Name, APEX_Status__c,
createdDate FROM APEX_Invoice__c WHERE createdDate = today];
List<apex_invoice__c> updatedInvoiceList = new List<apex_invoice__c>();
APEX_Customer__c objCust = new APEX_Customer__C();
objCust.Name = 'Test';

// Inserting the Customer Records
insert objCust;
for (APEX_Invoice__c objInvoice: invoiceList) {
   if (objInvoice.APEX_Status__c == 'Pending') {
      objInvoice.APEX_Status__c = 'Paid';
      updatedInvoiceList.add(objInvoice);
   }
}

// DML Statement to update the invoice status
update updatedInvoiceList;

// Prints the value of updated invoices
System.debug('List has been updated and updated values are' + updatedInvoiceList);

// Inserting the New Records using insert DML statement
APEX_Invoice__c objNewInvoice = new APEX_Invoice__c();
objNewInvoice.APEX_Status__c = 'Pending';
objNewInvoice.APEX_Amount_Paid__c = 1000;
objNewInvoice.APEX_Customer__c = objCust.id;

// DML which is creating the new record
insert objNewInvoice;
System.debug('New Invoice Id is' + objNewInvoice.id);

// Deleting the Test invoices from Database
// fetch the invoices which are created for Testing, Select name which Customer Name
// is Test.
List<apex_invoice__c> invoiceListToDelete = [SELECT id FROM APEX_Invoice__c
   WHERE APEX_Customer__r.Name = 'Test'];

// DML Statement to delete the Invoices
delete invoiceListToDelete;
System.debug('Success, '+invoiceListToDelete.size()+' Records has been deleted');

取消删除操作

您可以取消删除已删除并存在于回收站中的记录。已删除记录具有的所有关系也将被恢复。

示例

假设需要恢复在上一个示例中删除的记录。这可以使用以下示例实现。上一个示例中的代码已为此示例修改。

// fetch the invoice created today
List<apex_invoice__c> invoiceList = [SELECT id, Name, APEX_Status__c,
createdDate FROM APEX_Invoice__c WHERE createdDate = today];
List<apex_invoice__c> updatedInvoiceList = new List<apex_invoice__c>();
APEX_Customer__c objCust = new APEX_Customer__C();
objCust.Name = 'Test';

// Inserting the Customer Records
insert objCust;
for (APEX_Invoice__c objInvoice: invoiceList) {
   if (objInvoice.APEX_Status__c == 'Pending') {
      objInvoice.APEX_Status__c = 'Paid';
      updatedInvoiceList.add(objInvoice);
   }
}

// DML Statement to update the invoice status
update updatedInvoiceList;

// Prints the value of updated invoices
System.debug('List has been updated and updated values are' + updatedInvoiceList);

// Inserting the New Records using insert DML statement
APEX_Invoice__c objNewInvoice = new APEX_Invoice__c();
objNewInvoice.APEX_Status__c = 'Pending';
objNewInvoice.APEX_Amount_Paid__c = 1000;
objNewInvoice.APEX_Customer__c = objCust.id;

// DML which is creating the new record
insert objNewInvoice;
System.debug('New Invoice Id is '+objNewInvoice.id);

// Deleting the Test invoices from Database
// fetch the invoices which are created for Testing, Select name which Customer Name
// is Test.
List<apex_invoice__c> invoiceListToDelete = [SELECT id FROM APEX_Invoice__c
   WHERE APEX_Customer__r.Name = 'Test'];

// DML Statement to delete the Invoices
delete invoiceListToDelete;
system.debug('Deleted Record Count is ' + invoiceListToDelete.size());
System.debug('Success, '+invoiceListToDelete.size() + 'Records has been deleted');

// Restore the deleted records using undelete statement
undelete invoiceListToDelete;
System.debug('Undeleted Record count is '+invoiceListToDelete.size()+'. This should 
   be same as Deleted Record count');
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