Generating Parent Number using Level and Display Number

Question

I am facing problem in generating parent number using level and dispaly number.
Here is the table structure
CREATE TABLE test(
DISPLAY_NUMBER       NUMBER,
LEVEL_NUM           NUMBER,
COMPONENT   VARCHAR2(10))
INSERT INTO test VALUES (1,1,'A');
INSERT INTO test VALUES (2,2,'B');
INSERT INTO test VALUES (3,3,'C');
INSERT INTO test VALUES (4,4,'D');
INSERT INTO test VALUES (5,3,'E');
INSERT INTO test VALUES (6,3,'F');
INSERT INTO test VALUES (7,2,'G');
INSERT INTO test VALUES (8,3,'H');Here is the output table structure and required output data format
CREATE TABLE test1(
DISPLAY_NUMBER       NUMBER,
LEVEL_NUM           NUMBER,
COMPONENT   VARCHAR2(10),
PARENT VARCHAR2(10))
INSERT INTO test1 VALUES (1,1,'A',NULL);
INSERT INTO test1 VALUES (2,2,'B','A');
INSERT INTO test1 VALUES (3,3,'C','B');
INSERT INTO test1 VALUES (4,4,'D','C');
INSERT INTO test1 VALUES (5,3,'E','B');
INSERT INTO test1 VALUES (6,3,'F','B');
INSERT INTO test1 VALUES (7,2,'G','A');
INSERT INTO test1 VALUES (8,3,'H','B');Oracle database version : Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
Thanks in advance.
Regards,
Laxman

Answer 1

>
I am facing problem in generating parent number using level and dispaly number.
>
Thanks for posting the table DDL and data. I called the tables testa and testb.
insert into testb
select a.*, (select component from testa b where b.level_num + 1
  = a.level_num and rownum = 1) parent
from testa a
select * from testb
DISPLAY_NUMBER,LEVEL_NUM,COMPONENT,PARENT
1,1,A,
2,2,B,A
3,3,C,B
4,4,D,C
5,3,E,B
6,3,F,B
7,2,G,A
8,3,H,B