1. A computer program product comprising a computer readable storage 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 for each column of the fact table included in the join instructions, the frequency statistics retrieved from the catalog table, the frequency statistics table comprising a column for each join column of the fact table and a row for each distinct value in the one or more join columns; 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, the generated statistical view comprising a table structure formed by joining the generated frequency statistics table with the dimension table instead of joining the fact table with the dimension table and populating the statistical view with the estimated frequency statistics.
2. The computer program product of claim 1 , the operations further comprising sending the estimated frequency statistics to a cost based query optimizer.