It has most of the nutritional value it had before it was canned but some vitamins degrade pretty rapidly.

One of the factors in food preservation and nutrition is the stability of different vitamins. Specifically, there are water-soluble and fat-soluble vitamins.

Water-soluble vitamins dissolve in water. They are less stable and more affected by processing and include folate, thiamine, and vitamin C. Fat-soluble vitamins dissolve in fat. They’re more stable and include water, vitamin A, D, E, and K. Fat-soluble vitamins are less effected by cooking and preserving.

Basically it depends on what the food is and how it is preserved

If I'm honest with you though there is no harm in eating canned food and no such thing as "empty calories" all of your daily nutrients are important and you should get them but not meeting you daily quota isn't such a huge deal as long as it isn't especially consistent. Calories are your fuel but you can think of vitamins and micro nutrients as your oil that keeps things running smoothly.

If your diet is primarily canned goods I would recommend taking a multivitamin or altering your diet to include fresh produce containing those water soluble vitamins.