Maybe my 10000 rows are 5 tables, 2000 rows each, and I want to have some regular SQL features like joins? Can I do that without having to do joins in code? Bec

Maybe my 10000 rows are 5 tables, 2000 rows each, and I want to have some regular SQL features like joins? Can I do that without having to do joins in code? Because if I have to do joins in code, I can just store data in flat files and process everything in memory. But what if I want to have an existing app designed to run against a db system? If I have to start writing joins by hand, what's the point of even having a database?