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📜  Apex-DML

📅  最后修改于: 2020-11-05 03:14:26             🧑  作者: Mango

在本章中，我们将讨论如何在Salesforce中执行不同的数据库修改功能。有两个说法可以用来执行功能。

DML语句

DML是为了执行插入，更新，删除，向上插入，还原记录，合并记录或转换潜在顾客操作而执行的动作。

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对数据库的更改和修改。

数据库方法

您可以使用DML语句执行的所有操作也可以使用数据库方法执行。数据库方法是可用于执行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。

在本章中，我们将探讨使用DML语句的第一种方法。我们将在下一章中介绍数据库方法。

DML语句

现在让我们再次考虑化学品供应商公司的实例。我们的发票记录包含状态，已付金额，剩余金额，下次付款日期和发票编号等字段。今天已创建且其状态为“待处理”的发票应更新为“已付款”。

插入操作

插入操作用于在数据库中创建新记录。您可以使用Insert DML语句创建任何Standard或Custom对象的记录。

例

由于每天都会为新客户订单生成新发票，因此我们可以在APEX_Invoice__c对象中创建新记录。我们将首先创建一个客户记录，然后我们可以为该新客户记录创建发票记录。

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

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

// create List to hold the updated invoice records
List updatedInvoiceList = new List();
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

更新操作是对现有记录执行更新。在此示例中，我们将现有发票记录的“状态”字段更新为“已付费”。

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 invoiceList = [SELECT id, Name, APEX_Status__c,
createdDate FROM APEX_Invoice__c];
List updatedInvoiceList = new List();

// 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，如果数据库中不存在要更新的记录，则也要创建新记录。

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经存在，我们将对其进行更新，否则将创建一个新记录。这将基于字段APEX_External_Id__c的值。此字段将是我们的字段，用于识别记录是否已经存在。

注意-在执行此代码之前，请在Customer对象中创建一个记录，外部ID字段值为’12341’，然后执行以下代码-

// Example for upserting the Customer records
List CustomerList = new List();
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

您可以使用Delete DML执行删除操作。

例

在这种情况下，我们将删除为测试目的而创建的发票，即名称为“ Test”的发票。

您也可以从开发人员控制台执行此代码段，而无需创建类。

// fetch the invoice created today
List invoiceList = [SELECT id, Name, APEX_Status__c,
createdDate FROM APEX_Invoice__c WHERE createdDate = today];
List updatedInvoiceList = new List();
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 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。删除的记录所具有的所有关系也将恢复。

例

假设需要还原上一个示例中删除的记录。可以使用以下示例来实现。先前示例中的代码已针对此示例进行了修改。

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