A database server receives a data request from a client. In response to the data request, the database server selects, from a database, actual data that satisfies criteria specified by the data request. The database server retrieves the selected actual data from the database. Also in response to the data request, the database server redacts the retrieved data in real time without modifying the actual data contained within the database. This may be accomplished by the prior insertion of masking operators into a top SELECT clause of a query representation generated during semantic analysis. The database server returns the redacted data to the client as a reply to the data request.