1. A computer system comprising: a first computer having a first memory and being capable of executing a query; and a second computer having a second memory and being capable of executing said query, wherein said first computer: when stream data is received from an external device via a network and said query is to be executed, judges whether a first storage area for storing said stream data exists on said first memory; if said first storage area exists on said first memory, stores said stream data in said first storage area and executes said query by using data stored in said first storage area; if said first storage area does not exist on said first memory, transmits an identifier contained in said received stream data to said second computer; receives the data to be stored in said first storage area from said second computer; creates on said first memory said first storage area for storing said received data to be stored and said stream data; and executes said query by using data stored in said first storage area.