i think this originated from joe celko's sql for smarties: http://books.google.com/books?id=P1o4lxVnExsC&pg=PA340&lpg=PA340&dq=joe+celko+sql+smarties+sum+log+e

i think this originated from joe celko's sql for smarties: http://books.google.com/books?id=P1o4lxVnExsC&pg=PA340&lpg=PA340&dq=joe+celko+sql+smarties+sum+log+exp&source=bl&ots=0TYDWY7ZfI&sig=1WLg3_qyLEjXuHx7tm_TEvv14sQ&hl=en&ei=rPKaSpiXOoWesgOb1sWTDg&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=&f=false http://books.google.com/books?id=P1o4lxVnExsC&pg=PA340&#...