Hugo Kornelis (1/27/2010)
the strangely popular but really rather odd EXISTS 1 instead of EXISTS * (EXISTS checks for rows, not values, so what you put there is immaterial - except that * is the standard thhat anyone understands immediately while EXISTS(SELECT 1 makes everybody pause to think); and the broken link in the explanation (the two links both point to the same page).
I must admit I always use EXISTS (SELECT 'X' which is probably even more confusing! It's from my days with Oracle version 5 or 6 - in which we showed that * was slower than 1, by enough that it should be avoided, and that 1 was slightly slower than 'X' so we used the latter in preference. Old habits die hard...