1. A method for processing database data in a distributed database system, wherein the distributed database system comprises a plurality of computing nodes communicatively coupled via computer networks, the method comprising: creating a plurality of different data replicas wherein each of the data replicas is created in the following way: sorting the database data according to at least one data attribute; generating a row key based on the at least one data attribute; and using the sorted database data with the row key as the data replica, storing different data replicas in different computing nodes; and creating an index for each of the data replicas according to its row key.