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Need to Understand Explain plan [message #612733]

Thu, 24 April 2014 00:22

na.dharma@gmail.com
Messages: 82
Registered: May 2008
Location: bangalore

Member

Hi,

I am new to performance tuning. I need to understand the expalin plan output.
I did the following steps.
(1) Explain plan for
select e.empno, e.ename, d.dname
from emp e, dept d
where e.deptno = d.deptno
and e.deptno = 10;

Explained.

(2) SQL> SELECT * FROM table(dbms_xplan.display(null,null,'basic'));

PLAN_TABLE_OUTPUT
------------------------------------------------
Plan hash value: 568005898
------------------------------------------------
| Id | Operation | Name |
------------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | NESTED LOOPS | |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPT |
| 3 | INDEX UNIQUE SCAN | PK_DEPT |
| 4 | TABLE ACCESS FULL | EMP |
------------------------------------------------

Now What I need to do in order to increase the performance.
Please help.

Thanks in advanced

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Re: Need to Understand Explain plan [message #612734 is a reply to message #612733]

Thu, 24 April 2014 00:48

Michel Cadot
Messages: 68776
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Explain plan and its output is explained in Performance Tuning Guide
Chapter 19 Using EXPLAIN PLAN

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Re: Need to Understand Explain plan [message #612738 is a reply to message #612734]

Thu, 24 April 2014 02:40

cookiemonster
Messages: 13975
Registered: September 2008
Location: Rainy Manchester

Senior Member

If you want to try out techniques for improving performance you need to try them on queries that are actually slow. I very much doubt your example is slow.

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