Re: which column type char,varchar2 is better for index?

From: Daniel Morgan <damorgan_at_x.washington.edu>
Date: Thu, 10 Jun 2004 21:22:22 -0700
Message-ID: <1086927757.540852@yasure>

Jaguk Ku wrote:

> This is not the school work, i just curious about it.
> i can make table and index as you wish, and i might find out the
> differences, and the index structure algorithm from oracle documents.
> i think everyone can do this, what the newsgroup is for?
> if you don't want to answer the question. just ignore it. don't post the
> reply like this.
>
> Jaguk Ku
>
>
> "Daniel Morgan" <damorgan_at_x.washington.edu> wrote in message
> news:1086915921.985866_at_yasure...
>

>>Jaguk Ku wrote:
>>
>>
>>>hi there,
>>>
>>>if there are two columns A and B, A is defined as char(10), B is defined

>
> as
>

>>>varchar2(10)
>>>if when i create indexes for both of them. which one has better

>
> performance,
>

>>>and why?
>>>
>>>I think it's not much different, if the index is made with b-tree

>
> algorithm.
>

>>>Would anyone teach me what is different and which one is better and why?
>>>
>>>Thanks in advance,
>>>
>>>Jaguk Ku
>>
>>This is school work and your instructor expects you to build two
>>tables, create a loop, and test this out and learn from what you
>>observe.
>>
>>-- 
>>Daniel Morgan
>>http://www.outreach.washington.edu/ext/certificates/oad/oad_crs.asp
>>http://www.outreach.washington.edu/ext/certificates/aoa/aoa_crs.asp
>>damorgan_at_x.washington.edu
>>(replace 'x' with a 'u' to reply)

Well then let me say that this is exactly the type of exercise I give my students ... and I would suggest that you learn this the same way they do rather than asking the question.

But as I doubt you will let me give you the answer ... there is not a single valid reason I can think of in Oracle to ever use a CHAR column. And performance is only a small part of the reason.

Perhaps you can do some research and learn the rest of them.

-- 
Daniel Morgan
http://www.outreach.washington.edu/ext/certificates/oad/oad_crs.asp
http://www.outreach.washington.edu/ext/certificates/aoa/aoa_crs.asp
damorgan_at_x.washington.edu
(replace 'x' with a 'u' to reply)

Received on Thu Jun 10 2004 - 23:22:22 CDT