Select data based on condition

Within my database I have main members and associates, each account has a start and end date and all associates must be attached to a main member.
I need to know of any associates that still have a current account when their main member account has ended.
How do I create a statement that will display all associate accounts that do not have an end date but are attached to a main member that does?
Many thanks

What code have you written so far? (please post it).