You've probably received more comments than you want or need.  However, I will call your attention to a recent article in e-week (part of Ziff-Davis and connected to PC Magazine) comparing the top database programs:  Oracle, MS SQL, mySQL, and a few others.  Oracle and mySQL seemed to do the best when compared on performance, and when you consider the basically free price of mySQL, it did the best.  However, there were some differences that are worth knowing that don't necessarily make any one database the absolute best, as many Perl Monks have indicated above.

This e-week article was based on the results of an extensive comparison that they did amongst these databases.  They pushed the databases to extreme levels: for instance, they tested them for four weeks, retrieving something like up to 600 pages of data per minute for eight continuous hours per test to see if each database could hold up and to see how many pages of data they could retrieve per minute.

It's not a long article, but the process they went through and the results of their intensive testing is quite amazing.  It's a good background article for anyone who works with databases to read.

That's Spenser, with an "s" like the detective.