Trigger Apex Bulk DML on Trigger

relatedRecordOnAccount.cls

/**
 * The trigger fires after accounts are inserted or updated. The trigger adds a default opportunity for every account that doesn’t already have an opportunity. 
 */

trigger AddRelatedRecord on Account (after insert, after update) {

List<Opportunity> oppList = new List<Opportunity>();

// this will be determined by the operation type
List<Account> toProcess = null;

switch on Trigger.operationType {

  when AFTER_INSERT {
    toProcess = Trigger.New;
  }
  
  when AFTER_UPDATE 
    // SELECT account that don't already have a related opportunity
    toProcess = [Select Id, Name FROM Account WHERE Id IN :trigger.New AND Id NOT IN (Select AccountId FROM OPPORTUNITY WHERE AccountId IN :Trigger.NEW)];
    
  }
  

}

for (Account a : toProcess) {
  oppList.add(new Opportunity(Name = a.name + ' Opportunity', AccountId=a.Id));
}

if (oppList.size() > 0) {
  insert oppList;
}



}