I am new at sql and soql and need some help. I am trying to find out if a user record is marked out of office and if so add a backup user to their cases. I am having trouble with my query.

My Trigger

trigger myCaseTrigger on Case (before insert, before update) { Case[] cs = Trigger.new; caseChange.makeChange(cs); }

This is working for me as a test to change the case

public class caseChange { public static void makeChange(Case[] cs){ for (Case u : cs ) { if (u.Backup_User__c == null ) { u.Backup_User__c = u.OwnerId;} } } }

The next two are my attempt, but are not working

public class caseChange { public static void makeChange(Case[] cs){ for (Case u : cs ) { if (u.Owner__r.Out_Of_Office__c == 'true' ) { u.Backup_User__c = u.Owner__r.Backup_User__c;} } } }

public class caseChange { public static void makeChange(Case[] cs){ for (User u : cs ) { if (u.Out_Of_Office__c == 'true' ) { u.Cases__r.Backup_User__c = u.OwnerId;} } } }

Thank you for any advice or help.