1. A computer program product comprising a computer readable medium having: computer usable program code programmed to perform fast approximate computation of statistics on query expressions within a database management system (DBMS) by accurately estimating the sizes of intermediate query results based on frequency statistics, the operations of the computer program product comprising: analyzing a query expression for join instructions; identifying a fact table and a dimension table from the join instructions; retrieving frequency statistics from a catalog table corresponding to distinct values within one or more join columns of the fact table; generating a frequency statistics table comprising the frequency statistics retrieved from the catalog table; estimating frequency statistics corresponding to each column of a join result between the fact table and the dimension table by generating a statistical view comprising a join of the generated frequency statistics table and the dimension table by using the generated frequency statistics table to simulate the fact table; and populating the statistical view with the estimated frequency statistics.