Order within in Groups - Urgent please

Question

Hi,
Please let me know how can I achieve the following output.
I have following four tables,
COUNTRY_MASTER table contains SL_NO, COUNTRY_CODE, COUNTRY_NAME, .... columns.
STATE_MASTER table contains SL_NO, STATE_CODE, STATE_NAME, ... columns.
COUNTY_MASTER table contains SL_NO, COUNTY_CODE, COUNTY_NAME, ... columns.
CITY_MASTER table contains SL_NO, CITY_CODE, CITY_NAME, ... columns.
I have another mapping table,
MAPPING_TABLE table contains SL_NO, COUNTRY_SL_NO, STATE_SL_NO, COUNTY_SL_NO, CITY_SL_NO, ... columns.
I want output like this -
first column is LEVEL which contains 1 for Country, 2 for State, 3 for Country and 4 for City.
second column contains all countries, states, counties and cities (all should be in one column) ORDERED within groups for the second column.
There some other columns from other tables.
1 USA
2 MI
3 MONROE
4 MONROE
3 WAYNE
4 INKSTER
4 WAYNE
2 VA
3 HENRICO
4 RICHMOND
1 WEST INDIES
2 ...
I am working on Oracle 9i Release 2. Please help.
Thanks.

Answer 1

A cursor would be one way to handle this...loop through the rows or you could use decode like so:
select level, decode(level, 1, nvl(cr.country_name, 'NULL'),
                            2, nvl(st.state_name, 'NULL'),
                            3, nvl(ct.county_name, 'NULL'),
                               nvl(ci.city_name, 'NULL'))
  from country_master cr, state_master st, county_master ct, city_master ci
       ((select 1 level, t_country_sl_no, 0 t_state_sl_no, 0 t_county_sl_no, 0 t_city_sl_no
          from mapping_table
         group by country_sl_no)
        union all
        (select 2 level, t_country_sl_no, t_state_sl_no, 0 t_county_sl_no, 0 t_city_sl_no
          from mapping_table
         group by country_sl_no, state_sl_no)
        union all
        (select 3 level, t_country_sl_no, t_state_sl_no, t_county_sl_no, 0 t_city_sl_no
          from mapping_table
         group by country_sl_no, state_sl_no, county_sl_no)
        union all
        (select 4 level, t_country_sl_no, t_state_sl_no, t_county_sl_no, t_city_sl_no
          from mapping_table))
where t_country_sl_no = cr.country_sl_no
   and t_state_sl_no = st.state_sl_no (+)
   and t_county_sl_no = ct.county_sl_no (+)
   and t_city_sl_no = ci.city_sl_no (+)
order by cr.country_name, st.state_name, ct.county_name, ci.city_name;