String queryString = "SELECT * FROM ( " +
    "    SELECT  " +
    "        a_type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        lent_value as 'Credits', " +
    "        '' as 'Payment Info' " +
    "    FROM free_users " +
    "    UNION " +
    "    SELECT  " +
    "        type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        value as 'Credits', " +
    "        payment_info as 'Payment Info' " +
    "    FROM paid_users " +
    ") results " +
    "ORDER BY results.`Full Name` ";

Query query = entityManager.createNativeQuery(queryString);

query.getResultList();

String correctedQueryString = "SELECT * FROM ( " +
    "    SELECT  " +
    "        a_type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        lent_value as 'Credits', " +
    "        'p' as 'Payment Info' " +
    "    FROM free_users " +
    "    UNION " +
    "    SELECT  " +
    "        type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        value as 'Credits', " +
    "        payment_info as 'Payment Info' " +
    "    FROM paid_users " +
    ") results " +
    "ORDER BY results.`Full Name` ";