Just to elaborate on delis, or bodegas as they are commonly referred as in the Hispanic community near Columbia, is a small and local grocery store that sells cheap meals throughout the whole day. You can have a typical American breakfast such as eggs, bacon, pancakes, sausages, coffee and etc. My favorite part of delis is the option to buy cold cut sandwiches because they are relatively cheap and fast to make. Delis also offer hot sandwiches and other sides like potato salad, french fries and etc.
Okay I was going to hold my tongue, but for the good of the SDN community I'm going to give better foodie advice because it;s clear this person doesn't actually spend time where the dental school is. Most students live in the towers or really close to campus.
1. There are no bodegas within the Columbia "campus bubble" (west of Broadway from 167th to 172nd). The nearest is an 8-10 minute walk away and an unpopular choice when you're busy and have a limited time for lunch. You are very much in a bubble, with much better food options, so you'll learn right away the places that are within walking distance. Washington heights is known for bodegas OUTSIDE of our bubble, but if you actually spent time around campus it's clear that none exist that are convenient to get to. The dental school and "the Towers" (name for the tall student dorms) are allllll the way West, on Haven Ave. The most popular places to get breakfast are Hilltop Perk on Haven Ave ($3.00 bagels, really good), and Mike's Bagels on Broadway ($2.75 I think, but bad coffee). There is a Starbucks (really its a Barnes and Noble) that sells bagels as well and is RIGHT on campus if you're in a pinch, but they're not as good. There are also small food places within the academic buildings (cold sandwiches, the Hammer building has sushi!, lots of snacks and of course coffee).
I would say for lunch, popular places are: Hilltop Perk on Haven Ave (organic options, hot buffet for breakfast and lunch for $8.75/lb, sandwiches $9), Jou jou (chopped salad for $9, CASH ONLY, in between Broadway&Ft. Washington), Mike's Bagels (cold sandwiches $8, takes card), Chipotle, Como Pizza for a slice (really greasy for lunch though...), Tasty Deli (huge sandwiches, can't remember price), and Strokos (lots of organic options, salad bar, hot food, lots of sandwhich options...one of my favs), Thung Thai (great thai food)
You will probably be living on or very near campus (hopefully), so I know a lot of students pack their lunch in the mornings.
2. There is a green halal truck that has sat on campus (outside of Hammer on Ft. Washington/168th) for YEARS. I can literally see it now. How dare you say there is no halal around! They're very beloved, $6 for a chicken&lamb over rice plate. It's delicious.
3. There is a lack of good Asian food options in Washington Heights in general, unfortunately. There are 2 Chinese food places close by: Jade Garden (decent but not amazing), and Empire (has low ratings, seems sketch to me so I haven't tried). If you try to google map "Sushi", you'll see what I mean. There are no sushi places close to Columbia at all.
The area is only slightly dangerous if you go very very east on Broadway at NIGHT, and since there's not much there most people feel no need to venture there. Where the majority of students will be living, it's very, very safe. I have taken the subway to 168th at 3am and walked across campus - there is always police presence and people around because the hospital and ambulances are open. Also, there is a "safety ride" where if you are a Columbia student, you can call and give them your ID number and they'll come pick you up from where you are and take you to your dorm (from 10 minute radius, I believe...they won't pick you up from a midtown bar, haha). We get safety alerts whenever crimes happen to a Columbia student on campus - I don't think in 2 years I've ever received one from this area (ironically, all of the alerts have been from crimes happening downtown at the undergrad campus on 116th). The area is VERY SAFE, even if the people look different than the state you came from.
*Not a dental student. Hope this helps!