1. For employing a computer system to execute a query on a database, a method comprising: A) providing inputs to the computer system that represent a query that, applied to the database, defines a plurality of independent snowflake schemas; and B) employing the computer system to: i) compute, separately for each of the snowflake schemas, an access plan for obtaining from that schema's tables a record set that includes the data requested by the query from those tables; ii) compute an access plan for obtaining the query's results from the record sets in which execution of the access plans thus computed will result; iii) obtain the query's results by executing the access plan; and iv) generate an output that represents the query results thus obtained.