I agree with Gus... if there are any duplicates in Mytable02 according to the WHERE clause, the SELECT will find them and return them. Updates, however, will only update a row in MyTable01 only once no matter how many "identical" rows exist in MyTable02. Some loath that fact... I frequently count on it. Oracle won't even let you do it.
--Jeff Moden
Change is inevitable... Change for the better is not.