Query to get the records with same last name

Question

I need to write a single sql query to get all records with duplicate last_name's. For example, if tab1 has 4 records:
10     Amit     Kumar
20     Kishore          Kumar
30     Sachin     Gupta
40     Peter     Gabriel
then the query should return
10     Amit     Kumar
20     Kishore     Kumar
id, name,L_name being the 3 columns in table
Apprecite you help.
Thank you
Mary

Answer 1

SQL> create table mytable (id,name,l_name)
  2  as
  3  select 10, 'Amit', 'Kumar' from dual union all
  4  select 20, 'Kishore', 'Kumar' from dual union all
  5  select 30, 'Sachin', 'Gupta' from dual union all
  6  select 40, 'Peter', 'Gabriel' from dual
  7  /
Table created.
SQL> select id
  2       , name
  3       , l_name
  4    from ( select t.*
  5                , count(*) over (partition by l_name) cnt
  6             from mytable t
  7         )
  8   where cnt > 1
  9  /
                                    ID NAME    L_NAME
                                    10 Amit    Kumar
                                    20 Kishore Kumar
2 rows selected.Regards,
Rob.