Update a custom field on Account object if the account has any chid records using triggers.  I am trying to update the parent account record if the account has any child accounts.  The scenario is when a new account is created , it does not have any child accoounts.  We have some reporting that is built based on a flag field which looks for accounts if it has child accounts and we would like to set a flag on the parent account if a child exists.  I wrote the following trigger but it sets the child account field value and not the parent accoount field value.


trigger updateAccountChildFlag on Account(after insert, after update) {  
    if (trigger.isUpdate) {
        //Identify Child Account
        Set<Id> setAccountChangedIds = new Set<Id>();
        for (Account oAccount : trigger.new) {
            Account oOldAccount = trigger.oldMap.get(oAccount.Id);
            if (oAccount.ChildExists__c == false ) {
                setAccountChangedIds .add(oAccount.Id);
            }
        }
        //If any, get child account associated with each account
        if (setAccountChangedIds.isEmpty() == false) {
            List<Account> listChildAccounts = [SELECT Id, ParentId FROM Account WHERE ParentId IN :setAccountChangedIds];
            for (Account oAccount1 : listChildAccounts) {
                //Get Accounts
            //    oAccount = trigger.newMap.get(oAccount1.Id);
                //Set Address
                oAccount1.ChildExists__c = true;
            }
            //If any, execute DML command to save contact addresses
            if (listChildAccounts.isEmpty() == false) {
                update listChildAccounts;
            }
        }
    }
}

The intent is to update current active account record by looping through all accounts to see if the parent account has child based on parent id field.  if the result set is not empty then set a flag field indicating that the child account exists.