Of course, a part-time job is not a necessary condition for successfully completing college studies. Therefore, it doesn't matter if there is no suitable job opportunity. The key is to learn the knowledge of this major well.
I think good "useful jobs" include:
1. Find a job related to your major and help yourself apply what you have learned.
2. Lock your interests before entering the society. Some students major in A, but they always feel more interested in B. You can take advantage of the opportunity of working to learn more about A or B.
3. Work in your favorite enterprise and learn more about its corporate culture; Think of the person you admire as the boss at work and learn from him.
4. Use part-time job to cultivate their interpersonal relationship, team spirit and other qualities.