Need query for below requirement

Question

create table nsk_temp2 (num number,parent_num number,src_num number);
insert into nsk_temp2 values (1000,null,null);
insert into nsk_temp2 values (1001,1000,null);
insert into nsk_temp2 values (1002,1000,null);
insert into nsk_temp2 values (1010,null,1000);
insert into nsk_temp2 values (2001,1010,null);
insert into nsk_temp2 values (2002,1010,null);
num  parent_num  src_num
1000          
1001     1000     
1002     1000     
1010          1000
2001     1010     
2002     1010     
Expected output
num  parent_num  src_num
1000          
1001     1000     
1002     1000     
1010          1000
2001     1010     1001
2002     1010     1002
2001 -> parent is 1010 and 1010 src_num is 1000 and 1000 is parent for 1001 and 1002, so 1001 and 2001 are identical records

Answer 1

Hi,
This does what you requested:
WITH     got_r_num     AS
     SELECT     num, parent_num, src_num
     ,     ROW_NUMBER () OVER ( PARTITION BY  parent_num
                               ORDER BY          num
                       )         AS r_num
     FROM    nsk_temp2
SELECT       d.num, d.parent_num
,       NVL ( d.src_num
           , s.num
           )          AS src_num
FROM           got_r_num  d
LEFT OUTER JOIN      got_r_num  m  ON  m.num     = d.parent_num
LEFT OUTER JOIN      got_r_num  s  ON  s.parent_num     = m.src_num
                               AND s.r_num     = d.r_num
ORDER BY  d.num
;Whether or not it gets the right results for the right reasons, I can't say, since I know so little about the reasons.
If 1001 and 2001 are identical, aren 1001 and 2002 identical, too? Can the parent_num/num hierarchy extend beyond 2 levels? What would happen if 1000 had more, or fewer, children than 2000?