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help on indexes [message #290565] Sat, 29 December 2007 23:32 Go to next message
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
Re: help on indexes [message #290566 is a reply to message #290565] Sat, 29 December 2007 23:45 Go to previous messageGo to next message
vamsi kasina
Messages: 2107
Registered: October 2003
Location: Riyadh, Saudi Arabia
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
Re: help on indexes [message #290567 is a reply to message #290565] Sat, 29 December 2007 23:46 Go to previous messageGo to next message
BlackSwan
Messages: 25033
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?

Re: help on indexes [message #290580 is a reply to message #290565] Sun, 30 December 2007 01:30 Go to previous message
Michel Cadot
Messages: 64102
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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