DB Index Acess

[Former Member]

Hi,

I should appolizes in Advance for my Question, I am not sure this is a valid one but want to put it to you.

Does mentioning the Column with high cardinality first in a SQL query improve the data fetching or it is the same mentioned at any place.could any one please give me a broder explanation on which algorithm does a Search pattern use in fetching data from index with multiple columns.

Thanks and Regards,

Srikanth.

Edited by: srisun on Apr 28, 2010 9:29 AM

[Former Member · Accepted solution]

Hi Srikanth,

Check out note 912620 - FAQ: Oracle indexes

This might give you an idea how indexes are being used and how data is selected.

Kind regards,

Mark

[Former Member]

Thanks to you both

Edited by: srisun on Apr 28, 2010 11:31 AM

[stefan_koehler]

Hello Srisun,

> Does mentioning the Column with high cardinality first in a SQL query improve the data fetching or it is the same mentioned at any place

... your question is answered in sapnote #825653 - Point 10.

> could any one please give me a broder explanation on which algorithm does a Search pattern use in fetching data from index with multiple columns.

... check sapnote #750631 for the "Approximations for cost calculation of the CBO"...

If you want to know it deeply - read the book "Cost-Based Oracle Fundamentals" by J. Lewis:

http://www.amazon.com/Cost-Based-Oracle-Fundamentals-Experts-Voice/dp/1590596366

Regards

Stefan