When salmon is put into the can it is not cooked but it goes through a certain process involving heat which essentially gets rid of all the bacteria and parasites that can be harmful when ingested. Those who are hesitant about eating canned salmon will want to consider the fact that it is the exact same thing as eating canned tuna.
There are certain benefits to cooking salmon though, despite what you may have been told in the past. Certain nutrients in salmon actually require cooking in order to activate, though you will find that others disappear. It is just a trade off which you will have to be willing to make.