Well, define "table food"... lol. Anything salty, high in fat, sugars, preservatives ... most aren't good for us, let alone the dogs. Most fruits and veggies are fine (stay away from grapes though! I think onions and avacado's are bad too). Plain chicken breast, a lot of just plain meat would be fine for most pups. There's a list of "okay people foods" for dogs somewhere.
As far as Walmart goes, I highly doubt you'll find anything decent in there. If you have a Costco near you, you can look for Kirkland or 4health. Alot of Tractor Supply's and stores like that carry some better foods. Most have Taste of the Wild.
I like Acana and Fromm among others but those are my top right now.
I would actually prefer to feed all canned food if I could afford it.... I believe canned food is better for dogs, less preservatives, more moisture, usually more meat. Dry kibble does about as much for their teeth are humans eating hard pretzels would.
In fact, I've heard that a lot of the carbs in dry kibbles can add to teeth problems such as tarter, but don't know if there is in truth in that.