In the Security/Users folder in my database, I have a bunch of security groups, include \"MyApplication Users\". I need to check if I am (or another user is) in this group,
Checking yourself or the current user:
SELECT IS_MEMBER('[group or role]')
A result of 1 = yes,0 = no, and null = the group or role queried is not valid.
To get a list of the users, try xp_logininfo if extended procs are enabled and the group in question is a windows group :
EXEC master..xp_logininfo
@acctname = '[group]',
@option = 'members'