Problem in Image file using c#

Question

Hello every one,
i have very big problem .. i have one database where i m saving the Image file's Path ... i want that i just want to insert one image file against of one student... if student has not photo then i can store diffrent image like (N/A).. one thing i would tell u for one student have only one image... same image could not save for diffrent student... so i m not getting how can solve it.. should i make PK of Path columns... let me know hope u understand what i want ...

thanks in Advance