Duplicate records on formula column

Question

I have a dataset that I am trying to modify to remove the duplicates based on the previous record.
ID Name Number of Days
1 Bob 2
1 Jim 2
2 Harry 8
3 John 10
4 Mary 5
4 Sue 5
4 Billy 5
I want to show the second Number of Days record to zero if the previous ID is the same. How do I do that in regular SQL and not PL/SQL loop? What function(s) could I use? I am putting this in Oracle Reports and the dataset should look like this:
ID Name Number of Days
1 Bob 2
1 Jim 0
2 Harry 8
3 John 10
4 Mary 5
4 Sue 0
4 Billy 0

Answer 1

The actual table has many records and the real data
is taking the lowest ascending name. So if the
records are :
1 MARY 10
1 SUE 10
Then, it should print :
1 MARY 10
1 SUE 0how about this?
4 Mary 5
4 Sue 0
4 Billy 0
shouldn't be ?
4 Billy 5
4 Mary 0
4 Sue 0
then
SQL> with t as
  2  (select 1 id, 'Bob' name, 2 num from dual union all
  3  select 1, 'Jim', 2 from dual union all
  4  select 2, 'Harry', 8 from dual union all
  5  select 3, 'John', 10 from dual union all
  6  select 4, 'Mary', 5 from dual union all
  7  select 4, 'Sue', 5 from dual union all
  8  select 4, 'Billy', 5 from dual)
  9  select id,name,decode(id,prev_id,0,num) num
10   from
11       (select id,name,num,lag(id, 1, 0) OVER (partition by id ORDER BY id,name) prev_id
12       from t);
        ID NAME         NUM
         1 Bob            2
         1 Jim            0
         2 Harry          8
         3 John          10
         4 Billy          5
         4 Mary           0
         4 Sue            0
7 rows selected.added solution
Message was edited by:
devmiral