How to limit rows selected?

Hi everyone! What's the optimum way to extract say, 50 , rows from say, 100 customer data tables - the table names are not known until runtime, ie, a separate table contains the names of these 100 customer data tables? Each customer data table may contain 1000+ records/rows. The 50 rows fetched/selected must be the ones which have say, the lowest age among all the records in 100 customer data tables. Thanks in advance. Jamwal. Email: jamwal@quality.com