Recursive Sub-query Factoring vs Hierarchical Query

Question

Experts,
The below are two queries i am executing by using classical approach hierarchical and newest recursive sub-query.Problem is output was different for recursive sub-query factoring, as this is not showing parent-child approach, while connect by prior is showing parent-child fashion.Query 1, i am using hierarchical as it showing correct output parent-child approach, while Query 2 is displaying all the level 1 nodes and then level 2 nodes.I want query 2 output to be same as query 1.Please modify query 2 as required.
Note:The output of the both queries won't be in displayed as it was in sqlplus, or toad.Please copy and use in your command prompts.
QUERY 1:
with main as(select 1 id,'john' name,null mgrid from dual union all
select 2 id,'michael' name,null mgrid from dual union all
select 3 id,'peter' name,null mgrid from dual union all
select 4 id,'henry' name,1 mgrid from dual union all
select 5 id,'nick' name,2 mgrid from dual union all
select 6 id,'pao' name,3 mgrid from dual union all
select 7 id,'kumar' name,3 mgrid from dual union all
select 8 id,'parker' name,3 mgrid from dual union all
select 9 id,'mike' name,5 mgrid from dual),
select lpad(' ',2*(level-1))||name name,level from main start with mgrid is null connect by prior id=mgrid;
OUTPUT :
NAME LEVEL
john 1
henry 2
michael 1
nick 2
mike 3
peter 1
pao 2
kumar 2
parker 2
9 rows selected.
QUERY 2:
with main as(select 1 id,'john' name,null mgrid from dual union all
select 2 id,'michael' name,null mgrid from dual union all
select 3 id,'peter' name,null mgrid from dual union all
select 4 id,'henry' name,1 mgrid from dual union all
select 5 id,'nick' name,2 mgrid from dual union all
select 6 id,'pao' name,3 mgrid from dual union all
select 7 id,'kumar' name,3 mgrid from dual union all
select 8 id,'parker' name,3 mgrid from dual union all
select 9 id,'mike' name,5 mgrid from dual),
/*select lpad(' ',2*(level-1))||name name,level from main start with mgrid is null connect by prior id=mgrid;*/
secmain (id,name,mgrid,hierlevel) as(select id,name,mgrid,1 hierlevel from main where mgrid is null
union all
select m.id,m.name,m.mgrid,sm.hierlevel+1 from main m join secmain sm on(m.mgrid=sm.id))
cycle id set is_cycle to 1 default 0
select lpad(' ',2*(hierlevel-1))||name name,hierlevel from secmain;
OUTPUT :
NAME HIERLEVEL
john 1
michael 1
peter 1
henry 2
nick 2
parker 2
kumar 2
pao 2
mike 3
9 rows selected.

Answer 1

Hi,
What's wrong with Query 1? If it's producing the results you want, then why not use it?
One of the nice features of CONNECT BY is that the output is automatically presented in hierachical order. The only way I know of to get the results of a recursive WITH clause in any kind or order is to do it yourself. Here's one way:
WITH       secmain (id, name, mgrid, hierlevel, path)     AS
     SELECT  id
     ,     name
     ,     mgrid
     ,     1               AS hierlevel
     ,     RPAD (name, 10)          AS path          -- Assuming name is never longer than 10
     FROM      main
     WHERE      mgrid     IS NULL
    UNION ALL
         SELECT     m.id
     ,     m.name
     ,     m.mgrid
     ,     sm.hierlevel + 1
     ,     sm.path || RPAD (name, 10)
     FROM     main      m
     JOIN     secmain  sm  ON   (m.mgrid     = sm.id)
     CYCLE     id     -- Why do you need this if CONNECT BY NOCYCLE wasn't needed in Query 1?
     SET      is_cycle     TO 1
     DEFAULT 0
SELECT        lpad ( ' '
            , 2 * (hierlevel - 1)
            ) || name                 AS name
,       hierlevel
FROM        secmain
ORDER BY  path
;Sorry, I don't have an Oracle 11.2 database right now, so I can't test it.
Edited by: Frank Kulash on Nov 23, 2011 9:15 AM
I didn't know about the SEARCH clause, Use Dom's solution, above.