text: SELECT count(*)
  FROM ((SELECT DISTINCT
    c_last_name,
    c_first_name,
    d_date
  FROM store_sales, date_dim, customer
  WHERE store_sales.ss_sold_date_sk = date_dim.d_date_sk
    AND store_sales.ss_customer_sk = customer.c_customer_sk
    AND d_month_seq BETWEEN 1200 AND 1200 + 11)
        EXCEPT
        (SELECT DISTINCT
          c_last_name,
          c_first_name,
          d_date
        FROM catalog_sales, date_dim, customer
        WHERE catalog_sales.cs_sold_date_sk = date_dim.d_date_sk
          AND catalog_sales.cs_bill_customer_sk = customer.c_customer_sk
          AND d_month_seq BETWEEN 1200 AND 1200 + 11)
        EXCEPT
        (SELECT DISTINCT
          c_last_name,
          c_first_name,
          d_date
        FROM web_sales, date_dim, customer
        WHERE web_sales.ws_sold_date_sk = date_dim.d_date_sk
          AND web_sales.ws_bill_customer_sk = customer.c_customer_sk
          AND d_month_seq BETWEEN 1200 AND 1200 + 11)
       ) cool_cust
  