Apex - 数据库方法

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数据库类方法是使用 DML 语句的另一种方式，它比插入、更新等 DML 语句更灵活。

数据库方法和DML语句的区别

插入操作

通过数据库方法插入新记录也非常简单和灵活。让我们考虑前面的场景，其中我们使用 DML 语句插入了新记录。我们将使用数据库方法插入相同的内容。

例子

// Insert Operation Using Database methods
// Insert Customer Records First using simple DML Statement. This Customer Record will be
// used when we will create Invoice Records
APEX_Customer__c objCust = new APEX_Customer__C();
objCust.Name = 'Test';
insert objCust; // Inserting the Customer Records

// Insert Operation Using Database methods
APEX_Invoice__c objNewInvoice = new APEX_Invoice__c();
List<apex_invoice__c> InvoiceListToInsert = new List<apex_invoice__c>();
objNewInvoice.APEX_Status__c = 'Pending';
objNewInvoice.APEX_Customer__c = objCust.id;
objNewInvoice.APEX_Amount_Paid__c = 1000;
InvoiceListToInsert.add(objNewInvoice);
Database.SaveResult[] srList = Database.insert(InvoiceListToInsert, false);

// Database method to insert the records in List
// Iterate through each returned result by the method

for (Database.SaveResult sr : srList) {
   if (sr.isSuccess()) {
      // This condition will be executed for successful records and will fetch the ids 
      // of successful records
      System.debug('Successfully inserted Invoice. Invoice ID: ' + sr.getId());
      // Get the invoice id of inserted Account
   } else {
      // This condition will be executed for failed records
      for(Database.Error objErr : sr.getErrors()) {
         System.debug('The following error has occurred.');
         
         // Printing error message in Debug log
         System.debug(objErr.getStatusCode() + ': ' + objErr.getMessage());
         System.debug('Invoice oject field which are affected by the error:' 
            + objErr.getFields());
      }
   }
}

更新操作

现在让我们考虑使用数据库方法的业务案例示例。假设我们需要更新 Invoice 对象的状态字段，但同时我们还需要记录状态、失败记录 ID、成功计数等信息。这是使用 DML 语句无法实现的，因此我们必须使用数据库方法获取我们的运营状态。

例子

如果发票的状态为“待处理”且创建日期为今天，我们将更新发票的“状态”字段。

下面给出的代码将有助于使用 Database.update 方法更新发票记录。另外，在执行此代码之前创建一个发票记录。

// Code to update the records using the Database methods
List<apex_invoice__c> invoiceList = [SELECT id, Name, APEX_Status__c,
   createdDate FROM APEX_Invoice__c WHERE createdDate = today];

// fetch the invoice created today
List<apex_invoice__c> updatedInvoiceList = new List<apex_invoice__c>();
for (APEX_Invoice__c objInvoice: invoiceList) {
   if (objInvoice.APEX_Status__c == 'Pending') {
      objInvoice.APEX_Status__c = 'Paid';
      updatedInvoiceList.add(objInvoice);    //Adding records to the list
   }
}

Database.SaveResult[] srList = Database.update(updatedInvoiceList, false);
// Database method to update the records in List

// Iterate through each returned result by the method
for (Database.SaveResult sr : srList) {
   if (sr.isSuccess()) {
      // This condition will be executed for successful records and will fetch
      // the ids of successful records
      System.debug('Successfully updated Invoice. Invoice ID is : ' + sr.getId());
   } else {
      // This condition will be executed for failed records
      for(Database.Error objErr : sr.getErrors()) {
         System.debug('The following error has occurred.');
         
         // Printing error message in Debug log
         System.debug(objErr.getStatusCode() + ': ' + objErr.getMessage());
         System.debug('Invoice oject field which are affected by the error:' 
            + objErr.getFields());
      }
   }
}

在本教程中我们将只讨论插入和更新操作。其他操作与这些操作和我们在上一章中所做的非常相似。