The Cognos Content Store database has a lot of valuable information, however, it is not always so easy to find this information. The following query can be useful for returning USER, GROUP, and ROLE information from the Cognos Content Store database.

Be aware the database structures can be changed with any any patch, fixpack or hotsite to Cognos and the SQL may fail or return wrong results. There is a better method for returning this information by using the Cognos SDK. More info here.

Content Store version:
Cognos 8 running on an Oracle database (also works on Cognos 10)

--=============================================================
--  COGNOS CONTENT STORE QUERY (Oracle database)
--  Use to find list USERS, ROLES and GROUPS information
--=============================================================
 
WITH base_query AS
(select classid,
         cmobjects.cmid,
         cmobjects.pcmid,
         cmobjnames.name as groupname
    from cognos_c84.cmobjects , cognos_c84.cmobjnames
   where cmobjects.cmid = cmobjnames.cmid
     and classid in (26,54)
     and cmobjnames.mapdlocaleid = 24
  union
  select classid,
         cmobjects.cmid as cmid,
         cmobjects.pcmid,
         cmobjnames.name as groupname
    from cognos_c84.cmobjects , cognos_c84.cmobjnames
   where cmobjects.cmid = cmobjnames.cmid
     and cmobjects.cmid in
         (select distinct cmobjects.pcmid from cognos_c84.cmobjects)
     and cmobjnames.mapdlocaleid = 24)
, ctebuildpath (cmid,pcmid,groupname,Hlevel,classid,directory_path) AS
 (select base_query.cmid,
         base_query.pcmid,
         base_query.groupname,
         1 as Hlevel,classid,
         to_char(base_query.groupname) as directory_path
    from base_query
   where groupname = 'Cognos'
   union all
  select recur.cmid,
         recur.pcmid,
         recur.groupname,
         cte.Hlevel+1 as Hlevel,
         recur.classid,
         to_char(cte.directory_path || ' > ' || recur.groupname) as directory_path
    from base_query recur, ctebuildpath cte
   where cte.cmid = recur.pcmid)
SELECT v_user.first_name,
       v_user.last_name,
       v_user.ldap_id       as user_full_name,
       v_group.name,
       v_group.directory,
       v_group_user.cmid    as GROUP_ID,
       classid,
       v_group_user.refcmid user_id
  FROM cognos_c84.cmreford1 v_group_user
  LEFT OUTER JOIN (SELECT c33.cmid user_id,
                          UPPER(c33.NAME) ldap_id,
                          c1.surname last_name,
                          c1.givenname first_name,
                          c1.email email
                     FROM cognos_c84.cmobjprops1 c1
                     left outer join cognos_c84.cmobjprops33 c33
                       on c33.cmid = c1.cmid
                   UNION
                   SELECT cmobjprops1.cmid user_id,
                          UPPER(cmobjprops33.NAME) ldap_id,
                          cmobjprops1.surname last_name,
                          cmobjprops1.givenname first_name,
                          cmobjprops1.email
                     FROM cognos_c84.cmobjprops1,
                          cognos_c84.cmobjprops33
                    WHERE cmobjprops1.cmid = cmobjprops33.cmid) v_user
    ON v_group_user.refcmid = v_user.user_id
  LEFT OUTER JOIN (SELECT ctebuildpath.cmid cmid,
                          UPPER(ctebuildpath.groupname) name,
                          ctebuildpath.directory_path as directory,
                          classid
                     FROM ctebuildpath) v_group
    ON v_group.cmid = v_group_user.cmid

Thanks to Cognos with Hari for putting this together on a SQL Server Content Store.