global class BatchCalcFirstInvoice implements Database.Batchable<sObject>,Schedulable {



    String query = ' SELECT id,(SELECT Date_Invoice__c FROm Invoices__r WHERE Date_iNVOICE__C!=null ORDER BY Date_Invoice__c ASC LIMIT 1),First_Invoice__c FROM Account';


  global BatchCalcFirstInvoice() {

  }

  global Database.QueryLocator start(Database.BatchableContext BC) {
    return Database.getQueryLocator(query);
  }

  global void execute(Database.BatchableContext BC, List<sObject> scope) {
    List<Account> toUpdate = New List <Account> ();
    for(Account A: (List<Account>) scope) {
      if(!A.Invoices__r.isEmpty()){
        A.First_Invoice__c = A.Invoices__r[0].Date_Invoice__c;
        toUpdate.add(A);
            }
            if(A.Invoices__r.isEmpty()){
                A.First_Invoice__c=null;
                toUpdate.add(A);
            }
    }
    update toUpdate;
  }

  global void finish(Database.BatchableContext BC) {

  }
    public void execute(SchedulableContext context) {
        Database.executeBatch(this);
    }

}

string conServiceProvided = '%CURRENCY ACCOUNTS%';

    String query = 'SELECT Id,(SELECT id, Contract_Service_Provided__c, Date_Invoice__c From Invoices__r WHERE Contract_Service_Provided__c != null and (Not Contract_Service_Provided__c LIKE : conServiceProvided) ORDER BY Date_Invoice__c ASC LIMIT 1) FROM Account';

    global BatchFirstInvoiceasProductClient() {

    }

    global Database.QueryLocator start(Database.BatchableContext BC) {
        return Database.getQueryLocator(query);
    }

    global void execute(Database.BatchableContext BC, List<sObject> scope) {
        List<Account> toUpdate = New List <Account> ();
        for(Account A: (List<Account>) scope) {
            if(!A.Invoices__r.isEmpty()){
                A.First_Invoice_as_Product_Client__c = A.Invoices__r[0].Date_Invoice__c;
                toUpdate.add(A);
            }
        }
        update toUpdate;
    }
    global void finish(Database.BatchableContext bc){

    }

    global void execute(SchedulableContext sc) {
        BatchFirstInvoiceasProductClient batchable = new BatchFirstInvoiceasProductClient();
        Database.executeBatch(batchable, 50);
    }
}