A relational database management system (RDBMS) for servicing query statements from one or more client machines, using a relational data store and a multi-dimensional database (MDDB). The RDBMS includes a query interface which is adapted to receive query statements from the client machines, and to generate one or more query requests. The RDBMS includes a query handling mechanism which receives each request from the query interface, extracts a set of dimensions associated with the request, uses the dimensions to retrieve aggregated fact data from the MDDB, and forwards retrieved aggregated fact data to the query processing mechanism for subsequent processing. When the query processing mechanism of the RDBMS determines that servicing one or more query requests requires data stored in the relational tables, then the query handling mechanism automatically routes the requests to the relational data tables, so that data can be accessed from the relational tables and forwarded to the query processing mechanism for use in servicing the requests, in a manner transparent to the client machine. When the query processing mechanism determines that servicing one or more query requests requires aggregated data from the MDDB, then the query handling mechanism automatically routes the requests to the MDDB, so that data can be accessed from the MDDB and forwarded to the query processing mechanism for use in servicing the requests, in a manner transparent to the client machine.