used "primary key"

hello i'm quite new to mysql and i've got the following question: if i try to add an entry with a primary key that's alerady in use, do i get some kind of feedback from the database? if yes, how can i read it? thanks for your help regards stefan -- stefan ott cellular: +41.79.2459777 stefan@desire.ch phone: +41.62.8274115 http://stefan.desire.ch fax: +41.62.8274118 "life is a sexually transmitted disease with 100% mortality"