Sun, Oracle's sometimes best friend, turned into an Oracle competitor this morning when it said it was buying MySQL, the open source database that's part of the famous LAMP stack. It's paying a billion dollars. MySQL was supposed to go public this year but picked the easier monetization route. Sanford C. Bernstein estimates MySQL?s financial position at breakeven on $60 million-$80 million on trailing 12-month revenues although over 100 million copies of the database have been downloaded. Sun is paying $800 million cash for MySQL's stock and assuming about $200 million in options. But Sun has been known to overpay for acquisitions before. Remember its fatal $2 billion Cobalt Networks deal?