A method for validating a query result for a query of a database uses an index of the database. A selection of a set of source data from the database is received and a first hash operation is performed on the source data in the database resulting in a database hash value for the source data. A second hash operation is performed on the source data in the index resulting in an index hash value. The index hash value is compared with the database hash value, and a guarantee indication is provided for the source data in the index.