I spoke with a recruiter at a school career fair. After answering some simple, general computer science knowledge questions, I was offered a 30-minute interview the next week. There were two interviewers who were clearly code-savvy themselves. They asked what language I was most familiar with and then requested I use a separate language of their choice. The interview was not very challenging. After the interview, I was requested to resubmit my resume to their online portal.

Given two tables, one with customer names and ID numbers, and another with ID numbers, phone numbers, and phone type, write a SQL query that returns all customers with only a cellphone listed.