select store_num, count(*) custcount from (
select store_num, concat(area_code,phone_num), count(concat(area_code,phone_num))
from orders_p
where ord_date>='00000000' and ord_date<='20070128' and store_num=1
group by concat(area_code,phone_num)
) ordpsub group by store_num
+--------+-------------+--------+--------+---------------+--------+---------+--------+--------+--------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+--------+-------------+--------+--------+---------------+--------+---------+--------+--------+--------+
| 2 | DERIVED | orders_p| range | PRIMARY,order_date,store_number,date_store| PRIMARY| 14 | [NULL] | 139250 | Using where; Using temporary; Using filesort|
| 1 | PRIMARY | <derived2>| ALL | [NULL] | [NULL] | [NULL] | [NULL] | 20720 | Using temporary; Using filesort|
+--------+-------------+--------+--------+---------------+--------+---------+--------+--------+--------+