How to select rows with duplicate column values

Question

hi,
i have a table property_details which has these 2 columns customerno and propertyno a customer can have many properties and property number has to be unique. but somehow these property number has been duplicated at an earlier stage so i have for a customer with many properties the same property number
how i will select such records whose asset numbers are the same
for ex
customer no property no
a1300 1
a1300 1
a1300 1
a2330 10
a2330 10
a2330 10
kindly suggest me a solution

Answer 1

this example might be of help.
SQL> select * from employees;
YEAR EM NAME       PO
2001 02 Scott      91
2001 02 Scott      01
2001 02 Scott      07
2001 03 Tom        81
2001 03 Tom        84
2001 03 Tom        87
6 rows selected.
SQL> select year, empcode, name, position,
  2         row_number() over (partition by year, empcode, name
  3                            order by year, empcode, name, position) as rn
  4    from employees;
YEAR EM NAME       PO         RN
2001 02 Scott      01          1
2001 02 Scott      07          2
2001 02 Scott      91          3
2001 03 Tom        81          1
2001 03 Tom        84          2
2001 03 Tom        87          3
6 rows selected.
SQL> Select year, empcode, name, position
  2    From (Select year, empcode, name, position,
  3                 row_number() over (partition by year, empcode, name
  4                                    order by year, empcode, name, position) as rn
  5            From employees) emp
  6   Where rn = 1;
YEAR EM NAME       PO
2001 02 Scott      01
2001 03 Tom        81
SQL>