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help on indexes [message #290565]

Sat, 29 December 2007 23:32

sd_md_rizwan@yahoo.com
Messages: 37
Registered: September 2007
Location: Saudi Arabia

Member

hi this is Syed Mohammed Rizwan,
when we create index for a large table contains some 10 lacks records and more then creating
the index for all columns is good or creating index for onle some columns like emp_num,
branch_num is good, which one gives me the best performance

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Re: help on indexes [message #290566 is a reply to message #290565]

Sat, 29 December 2007 23:45

vamsi kasina
Messages: 2112
Registered: October 2003
Location: Cincinnati, OH

Senior Member

Creating index on all columns will perform badly.
While DML it is a headache.
Create index only on required columns (for ex. high selectivity columns).
By the way most of them don't know that 10 lacks is a million, please use thousands, millions, billions, etc.

By
Vamsi

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Re: help on indexes [message #290567 is a reply to message #290565]

Sat, 29 December 2007 23:46

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

>which one gives me the best performance
It depends.
What is the actual SQL?
How many unique values of each?
On many other factors.

What did your benchmark test show was best?

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Re: help on indexes [message #290580 is a reply to message #290565]

Sun, 30 December 2007 01:30

Michel Cadot
Messages: 68665
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

Only create indexes that will speed up the query you will execute without too much decrease performances on DML.

Regards
Michel

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