Group by help please

Question

Oracle 11.2.0.1
Windows xp
create table cust(cust_id number,phone number,city varchar2(20),state varchar2(20),country varchar2(20));
insert into cust values (101,12345,'City1','State1','Country1');
insert into cust values (102,1114,'City1','State1','Country1');
insert into cust values (103,1214,'City2','State1','Country1');
insert into cust values (104,44414,'City2','State1','Country1');
insert into cust values (105,21454,'City2','State1','Country1');
insert into cust values (106,12546,'City1','State2','Country1');
insert into cust values (107,146,'City1','State2','Country1');
insert into cust values (108,44569,'City1','State2','Country1');
insert into cust values (109,26548,'City2','State2','Country1');
insert into cust values (110,96545,'City3','State2','Country1');
insert into cust values (111,945,'City1','State1','Country2');
SQL> select * from cust;
   CUST_ID      PHONE CITY                 STATE                COUNTRY
       101      12345 City1                State1               Country1
       102       1114 City1                State1               Country1
       103       1214 City2                State1               Country1
       104      44414 City2                State1               Country1
       105      21454 City2                State1               Country1
       106      12546 City1                State2               Country1
       107        146 City1                State2               Country1
       108      44569 City1                State2               Country1
       109      26548 City2                State2               Country1
       110      96545 City3                State2               Country1
       111        945 City1                State1               Country2
11 rows selected.Required output : (If I wish to get State=State1 and Country=Country1) Only any one row from each city of country1 and State1.
   CUST_ID      PHONE CITY                 STATE                COUNTRY
       101      12345 City1                State1               Country1
       103       1214 City2                State1               Country1Required output : (If I wish to get State=State2 and Country=Country1) Only any one row from each city of country1 and State2.
   CUST_ID      PHONE CITY                 STATE                COUNTRY
       106      12546 City1                State2               Country1
       109      26548 City2                State2               Country1
       110      96545 City3                State2               Country1any row i.e. columns of the table group by country,state,city.
Thanks.

Answer 1

Analytic functions are essential if you use SQL professionally. Here, you can also use grouping though.
SQL> SELECT Max (cust_id) KEEP (DENSE_RANK FIRST ORDER BY cust_id) cust_id,
  2         Max (phone) KEEP (DENSE_RANK FIRST ORDER BY cust_id) phone,
  3         city, state, country
  4    FROM cust
  5   GROUP BY country, state, city
  6   ORDER BY country, state, city, cust_id
  7  /
CUST_ID      PHONE CITY       STATE      COUNTRY
    101      12345 City1      State1     Country1
    103       1214 City2      State1     Country1
    106      12546 City1      State2     Country1
    109      26548 City2      State2     Country1
    110      96545 City3      State2     Country1
    111        945 City1      State1     Country2
6 rows selected.