Query for getting combination of data

Question

hi all,
i am using db10g.
i have a table of fields a_company,a_code,a_name,a_port,a_t_port,a_rate,a_volume
i have a records like
MM,AA,A-NAME,EFG,EFGH,100,20
MM,AA,A-NAME,EFG,EFGH,200,10
MM,BB,B-NAME,HIJ,HIJK,100,20
MM,BB,B-NAME,HIJ,HIJK,200,30
MM,CC,C-NAME,DEF,DEFG,500,20i have to select all columns but the fields if below below combination repeates(having more than 1 combination)
a_company,a_code,a_port,a_t_port
how can form a query?
in other words i am expecting the result like below among above said input.
MM,AA,A-NAME,EFG,EFGH,100,20
MM,AA,A-NAME,EFG,EFGH,200,10
MM,BB,B-NAME,HIJ,HIJK,100,20
MM,BB,B-NAME,HIJ,HIJK,200,30Thanks..

Answer 1

With only one table scan:
SQL> create table a_table (a_company,a_code,a_name,a_port,a_t_port,a_rate,a_volume)
  2  as
  3  select 'MM','AA','A-NAME','EFG','EFGH',100,20 from dual union all
  4  select 'MM','AA','A-NAME','EFG','EFGH',200,10 from dual union all
  5  select 'MM','BB','B-NAME','HIJ','HIJK',100,20 from dual union all
  6  select 'MM','BB','B-NAME','HIJ','HIJK',200,30 from dual union all
  7  select 'MM','CC','C-NAME','DEF','DEFG',500,20 from dual
  8  /
Table created.
SQL> exec dbms_stats.gather_table_stats(user,'a_table')
PL/SQL procedure successfully completed.
SQL> set autotrace on explain
SQL> select a_company
  2       , a_code
  3       , a_name
  4       , a_port
  5       , a_t_port
  6       , a_rate
  7       , a_volume
  8    from ( select a.a_company
  9                , a.a_code
10                , a.a_name
11                , a.a_port
12                , a.a_t_port
13                , a.a_rate
14                , a.a_volume
15                , count(*) over (partition by a_company,a_code,a_port,a_t_port) cnt
16             from a_table a
17         )
18   where cnt > 1
19  /
A_ A_ A_NAME A_P A_T_     A_RATE   A_VOLUME
MM AA A-NAME EFG EFGH        100         20
MM AA A-NAME EFG EFGH        200         10
MM BB B-NAME HIJ HIJK        100         20
MM BB B-NAME HIJ HIJK        200         30
4 rows selected.
Execution Plan
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=4 Card=5 Bytes=330)
   1    0   VIEW (Cost=4 Card=5 Bytes=330)
   2    1     WINDOW (SORT) (Cost=4 Card=5 Bytes=140)
   3    2       TABLE ACCESS (FULL) OF 'A_TABLE' (Cost=2 Card=5 Bytes=140)Regards,
Rob.