Query optimisation

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how is canonical tree constructed a given SQL query? How to optimize this tree?

Posted 11-Dec-09 2:36am

Md.Ejaz

Updated 18-Jan-10 8:18am

thatraja

v2

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deepika.tella · Answer 1 · 2011-06-08T08:03:00

Hi Oracle provides Pseudo column Connect by Prior...

example:1
select name, slave_id, supervisor_id
from corporate_slaves
connect by prior slave_id = supervisor_id;

example:2
select /*+ first_rows */
rpad( '*', (level-1)*2, '*' ) ||
ename ename, empno, mgr_key
from emp
start with mgr_lookup(mgr_key) = -1
connect by prior empno = mgr_lookup(mgr_key);

hope it helps you...