Oracle SQL WITH clause connect by isleaf

Also see my Oracle recursive WITH clause notes.

Oracle connect by isleaf

Oracle author Laurent Schneider has this great explanation of the Oracle connect by isleaf syntax:

The 10g query using connect_by_isleaf:

 

with o as

(

SELECT 'A' obj, 'B' link from dual union all

SELECT 'A', 'C' from dual union all

SELECT      'C', 'D' from dual union all

SELECT           'D', 'C' from dual union all

SELECT           'D', 'E' from dual union all

SELECT                'E', 'E' from dual)

select connect_by_root obj root,level,obj,link,

  sys_connect_by_path(obj||

'->'

||link,','),

  connect_by_iscycle,

  connect_by_isleaf

from o

connect by nocycle obj=prior link

start with obj='A';

 

ROOT LEVEL O L PATH                 CYCLE  LEAF

---- ----- - - -------------------- ----- -----

A        1 A B ,A->B                    0     1

A        1 A C ,A->C                    0     0

A        2 C D ,A->C,C->D               1     0

A        3 D E ,A->C,C->D,D->E          1     1

Obviously in 10g the connect by nocycle does works well with that kind of graphs, D-C and E-E are missing and C-D and D-E are marked as cycling…

Let’s try the 11gR2 equivalency.

 

with o(obj,link) as

(

SELECT 'A', 'B' from dual union all

SELECT 'A', 'C' from dual union all

SELECT      'C', 'D' from dual union all

SELECT           'D', 'C' from dual union all

SELECT           'D', 'E' from dual union all

SELECT                'E', 'E' from dual),

t(root,lev,obj,link,path) as (

select obj,1,obj,link,cast(obj||'->'||link

as varchar2(4000))

from o

where obj='A'  -- START WITH

union all

select

  t.root,t.lev+1,o.obj,o.link,

  t.path||', '||o.obj||

    '->'

    ||o.link

from t, o

where t.link=o.obj

)

search depth first by obj set ord

cycle obj set cycle to 1 default 0

select root,lev,obj,link,path,cycle,

    case

    when (lev - lead(lev) over (order by ord)) < 0

    then 0

    else 1

    end is_leaf

 from t;

 

ROOT LEV  OBJ  LINK PATH                        CYCLE IS_LEAF

---- ---- ---- ---- --------------------------- ----- -------

A    1    A    B    A->B                            0       1

A    1    A    C    A->C                            0       0

A    2    C    D    A->C, C->D                      0       0

A    3    D    C    A->C, C->D, D->C                0       0

A    4    C    D    A->C, C->D, D->C, C->D          1       1

A    3    D    F    A->C, C->D, D->E                0       0

A    4    F    F    A->C, C->D, D->E, E->E          0       0

A    5    F    F    A->C, C->D, D->E, E->E, E->E    1       1

Guarantee your Success! Oracle is the world's most complex, robust and flexible database, considered impossible to master without a mentor. That's why all BC Oracle trainers are working professionals, experts in Oracle who share their tips and secrets.

Burleson is the American Team Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum. Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications. Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  and include the URL for the page.                      Burleson Consulting The Oracle of Database Support Oracle Performance Tuning Remote DBA Services   Copyright ? 1996 -  2011 by Burleson Enterprises All rights reserved. Oracle ? is the registered trademark of Oracle Corporation.