Thank you both. We were able to get it working using the query below.

select userkey from users where FIND_IN_SET(users.'value', (select raa.ATTRIBUTE_VALUE from request_access_attrs raa , ars_requests ar, request_access ra WHERE ra.REQUESTKEY = ar.REQUESTKEY and raa.REQUEST_ACCESS_KEY = ra.REQUEST_ACCESSKEY and raa.ATTRIBUTELABLE= 'label name' and ar.REQUESTKEY = ${ARSREQUEST.id})) !=0