I use MySQL and SQL Server everyday and there isn't a really huge difference in performance. And I'm working with large (100 line) queries over large sets of data trying to return real-time results. I've got more joins, subselects, and unions going on than the average user will ever use and I still return results instantly.

Now older versions of MySQL, like 3.23, are still in use (unfortunately) and pretty crappy but it was released over 8 years ago. Most of these performance myths about MySQL are outdated.

Last time I checked, and feel to correct me if I am wrong, MySQL used Row lookups when doing JOINs. There was no support for more efficient join algorithms like hash-join or merge-join, something which kills performance if you intend to run JOINs on a result/working-set bigger than just a few rows.

Are there any improvements in this area, or is it still just the same old, same old?