Please help me regarding the WITH RECURSIVE query

Hello All,

I am migrating oracle queries to postgres queries

*Oracle query is below*

select * from (select * from KM_COURSE_MAST where ID in (select OBJ_ID from
(select OBJ_ID,PERFORMER_TYPE,PERFORMER_ID from KM_REL_OBJ_PER_ACTION
where OBJ_TYPE='COURSETYPE') where PERFORMER_TYPE='GROUP' and PERFORMER_ID
in (select PARENT_ID from KM_REL_SELF_GROUP start with CHILD_ID in ( SELECT
GROUP_ID FROM KM_REL_GRP_USER WHERE USER_ID=52247) connect by CHILD_ID=
prior PARENT_ID union SELECT GROUP_ID PARENT_ID FROM KM_REL_GRP_USER WHERE
USER_ID=52247)) union select * from KM_COURSE_MAST where CREATED_BY=52247)
order by DISPLAYORDER
*
*
*We have changed to postgres query like below*
*
*
select * from (select * from KM_COURSE_MAST where ID in (select OBJ_ID from
(select OBJ_ID,PERFORMER_TYPE,PERFORMER_ID from KM_REL_OBJ_PER_ACTION
where
OBJ_TYPE='COURSETYPE') g where PERFORMER_TYPE='GROUP' and PERFORMER_ID in
(WITH RECURSIVE parents as ( select PARENT_ID from KM_REL_SELF_GROUP where
CHILD_ID in ( SELECT
GROUP_ID FROM KM_REL_GRP_USER WHERE USER_ID=52247) UNION select a.PARENT_ID
FROM KM_REL_SELF_GROUP a ,*parents p *where a.CHILD_ID = p.PARENT_ID )
select PARENT_ID from parents order by
PARENT_ID asc)) union select * from KM_COURSE_MAST where
CREATED_BY='52247') KM_COURSE_MAST where ID =214

Above postgres query will work fine if resultset has multiple tuples but
returns empty if result set has single row.

Again i have changed above query like below

select * from (select * from KM_COURSE_MAST where ID in (select OBJ_ID from
(select OBJ_ID,PERFORMER_TYPE,PERFORMER_ID from KM_REL_OBJ_PER_ACTION
where
OBJ_TYPE='COURSETYPE') g where PERFORMER_TYPE='GROUP' and PERFORMER_ID in
(WITH RECURSIVE parents as ( select PARENT_ID from KM_REL_SELF_GROUP where
CHILD_ID in ( SELECT
GROUP_ID FROM KM_REL_GRP_USER WHERE USER_ID=52247) UNION select a.PARENT_ID
FROM KM_REL_SELF_GROUP a ,*KM_REL_SELF_GROUP* *p *where a.CHILD_ID =
p.PARENT_ID ) select PARENT_ID from parents order by
PARENT_ID asc)) union select * from KM_COURSE_MAST where
CREATED_BY='52247') KM_COURSE_MAST where ID =214

It returns resultset with single row

Please explain me why it is ?

Thanks,
Gajendra