USERS(uid,name)   USERS_GROUPS(u_id,r_id,flag)       REQUESTS(rid,status)
------------------------------------------------------------------------
1  John             1  96   1                       96    0
2  Peter            1  97   1                       97    0
3  Helen            2  97   0                       98    0
                    3  97   0                       99    1
                    2  98   1
                    1  98   0
                    3  98   0

1  96   1
1  97   1
2  97   0
3  97   0