from t1,t2,t3
where t1.id = t2.id(+)
and t2.id = t3.id(+)
--order by 1
;
T1_ID T2_ID T3_ID
---------- ---------- ----------
1 1 1
3
2 2
select t1.id t1_id, t2.id t2_id, t3.id t3_id
from t1
left join t2 on t1.id = t2.id
left join t3 on t3.id = t2.id
--order by 1
;
T1_ID T2_ID T3_ID
---------- ---------- ----------
1 1 1
3
2 2
Observation: They return same result.
Fyi, init testing data.
drop table t1 purge;
drop table t2 purge;
drop table t3 purge;
create table t1 (id number);
create table t2 (id number);
create table t3 (id number);
insert into t1(id) select rownum from dual connect by level <= 3;
insert into t2(id) select rownum from dual connect by level <= 2;
insert into t3(id) select rownum from dual connect by level <= 1;
commit;
