Combobox dependent on a table

Hello, I need help to create a combobox dependent
I have a table called "COLLEGE", within her own columns:
 
COL_ID
COL_Name
COL_USER
COL_IMAGE

How should work:
- The first combo will list all data in the column "col_name";
- When you select any name of the first combo, the second combo should be automatically populated with information from the column "COL_IMAGE"

I am seen in some tutorials that you should use two tables, but in my case I want to use only one. Help me?