SQL is Faster: Recently I have been optimising some reports by using dummy temporary tables from within my programs.
About 14 years ago, I converted a large business system that was using ISAM based tables, to SQL. One report they were running daily from 30 minutes to less than 10 seconds to produce the needed data. Happy customers. They thought I was magic, but it was all due to the switch to using SQL as the database engine.
If you are still programming and using ISAM files for data tables, consider switching to SQL. I use Microsoft SQLServer. It just works so well.