Trigger new apex - list

Question

I am trying to write a Trigger for before insert event on Account object.
trigger DeduplicationAccount on Account (before insert) {
//Get all the accounts in action in 'insert'
Account[] inputAccountList = Trigger.NEW;
I am trying to get a relative list of accounts in my input list of accounts.
Say for eample, I am trying to get such accounts where the last name = 'XXX' in my trigger new.
So, i am writing like this:
// Here, listOfSurname is containing a list of surname with 'XXX'
for(Account ac: Trigger.new){
List<Account> accountDuplicate = [Select ac.rr_First_Name__c, ac.rr_Last_Name__c From
Account ac where ac.rr_Last_Name__c IN : listOfSurname];
System.debug('accountDuplicate: '+ accountDuplicate);
}
But, this list is always coming as 0 though im my input,an account have surname as 'XXX'.

Answer 1

Trigger.New has all the information for the record and we could use that to verify against any condition. I rephrased your query below to check if each account's lastname in Trigger.new is part of the list.
for(Account ac: Trigger.new){
for(String s: listOfSurname){
if (ac.rr_Last_Name__c == s){
System.debug('accountDuplicate: '+ ac);
break;
}
}
}