Re: which should be faster

Comment in line

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Jonathan Lewis
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: 02 May 2003 22:12

> general rule: put most selective column first in concatenated indexes.
>

This is a well-known myth.

General rule - identify the column order dictated by the most important query requirements. (e.g. columns usually involved in range scans TEND to be placed towards the end of the index)

All other things being equal - consider ordering the columns to maximise the benefit of index compression and (for Oracle 9) maximise the option for index skip scans. (i.e. least selective first).

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