When you buy chickpeas in a can the canned chickpeas are already fully cooked and not raw so you can eat the canned chickpeas straight out of the can without heating them up.
I like to heat my canned chickpeas up though because I find they taste better than cold chickpeas but you can safely eat chickpeas without heating them up.
Eating raw chickpeas can be hard on your digestive system and increase flatulence and be potentially poisonous.
If you have raw chickpeas soak them overnight in a bowl of water and cook them before eating but canned chickpeas are already cooked and ready to eat.