An SQL interceptor inserted as a proxy between a database client and the corresponding database server intercepts a constrained application-generated SQL query and composes a new data request. Parameter values in the SQL query determine whether the new data request is sent to a database server or a web service provider. A reserved table name specified in the SQL query triggers a rewrite of the data request. Parameter values in the query are used to select among a plurality of executable modules to use for rewriting the data request. Special data encoding and formats need to be used based on the source of data that will receive and respond to the rewritten data request. For example, communication between a database client and server may use a vendor-specific, non-standard binary encoding, and XML and JSON response data must be reformatted as an SQL response for processing by the database client.