SELECT
        cu.customer_name2
    FROM 
        customer cu
    WHERE 
        cu.customer_name2 <> ''
        AND cu.customer_group = ''
        AND cu.customer_code IN (
            SELECT customer_code FROM reading_group_customer
            WHERE customer_group = '' AND any_code = ''
        )
    GROUP BY
        cu.customer_name2
    ORDER BY 
        cu.customer_name2