Earning Points. Starwood's Preferred Guest program is fairly straightforward: the more nights you spend at participating hotels, the faster you'll earn a free night.
The mapper output (intermediate data) is stored on the Local file system (NOT HDFS) of each individual mapper nodes. This is typically a temporary directory location which can be setup in config by the hadoop administrator. The intermediate data is cleaned up after the Hadoop Job completes.
A mapping table is required in order to implement such a relationship. For example, all the customers belonging to a bank is stored in a customer table while all the bank's products are stored in a product table. Each customer can have many products and each product can be assigned to many customers.