Re: Performance question

For the LAST time

> My question though, once again, is the LENGTH the length the 'n' in the
> VARCHAR (n) definition, or is the length the actual bytecount? If it is
the
> actual bytecount, then where does the 'n' from the definition stored?

the length is the ACTUAL BYTECOUNT
the maximum bytecount gets stored in the dictionary, in user_tab_columns.

Regards

--
Sybrand Bakker
Senior Oracle DBA

to reply remove '-verwijderdit' from my e-mail address



"Eric Levinson" <nospam_at_nospam.com> wrote in message
news:4LbJ8.4858$3w2.22336_at_typhoon.sonic.net...


> I can't find it.  I am looking in a Oracle 7 guide in appendix A

> "Initialization Parameters" but it isn't there.

>

> I found something online which shows:

>

> COLUMN NAME      = TICKER

>        TYPE      = VARCHAR2

>        LENGTH    = 10

>        PRECISION =

>        SCALE     =

>

>

> As an example.

>

> My question though, once again, is the LENGTH the length the 'n' in the

> VARCHAR (n) definition, or is the length the actual bytecount?  If it is

the


> actual bytecount, then where does the 'n'  from the definition stored?

>

>

> "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote in message

> news:ufafin8tr37ue0_at_corp.supernews.com...

> > The length is stored with the data, expect for date columns (fixed

length


> of

> > 7 bytes).

> > This used to be in Appendix A of the Oracle Server Administrators

Manual.


> A

> > search on 'datatypes' on http://tahiti.oracle.com will probably provide

> the

> > correct reference.

> >

> > Hth

> >

> >

> > --

> > Sybrand Bakker

> > Senior Oracle DBA

> >

> > to reply remove '-verwijderdit' from my e-mail address

> >

> > "Eric Levinson" <nospam_at_nospam.com> wrote in message

> > news:%h8J8.4759$3w2.21577_at_typhoon.sonic.net...

> > > Oops, I made a mistake, you were confirming my original quesiton, that

> > yes,

> > > the length of the column is stored with the data, can anyone else

> confirm

> > > this?  Is this documented in any Oracle documentation?  I can't find

it


> > > anywhere.

> > >

> > > Thanks,

> > >

> > > Eric

> > >

> > > "Eric Levinson" <nospam_at_nospam.com> wrote in message

> > > news:ie8J8.4757$3w2.21689_at_typhoon.sonic.net...

> > > > Thanks for your answer, Howard, however it was not what I was

asking.


> > > >

> > > > For CHAR(10), what you stated applies.

> > > > For VARCHAR(10), the column is variable size regardless of the "10"

> > > >

> > > > My question is, if I store the word 'test' in a VARCHAR2(10) column,

> is

> > > > there another piece of data ONLY for varchar2 or any other datatype

> > which

> > > is

> > > > variable width which would store the number 4, so that LENGTH

returns


> > this

> > > > value, or is this data NOT stored, and everytime LENGTH function is

> > > called,

> > > > the database has to count characters in the VARCHAR2 field till it

> > reaches

> > > > some end of field mark (like hex FF)

> > > >

> > > >

> > > > Thanks,

> > > > Eric

> > > >

> > > >

> > > >

> > > > "Howard J. Rogers" <dba_at_hjrdba.com> wrote in message

> > > > news:ad14go$gkk$1_at_lust.ihug.co.nz...

> > > > > The format of a row is: row header, column length - value; column

> > > length -

> > > > > value; column length - value; and so ad infinitum (nearly).

> > > > >

> > > > > The length of a field is stored as an attribute within the row. If

> it

> > > was

> > > > > Name Char(10) it would be stored as :10:Smith-----: If it was Name

> > > > > varchar2(10) it would be stored as :5:Smith:

> > > > >

> > > > > Regards

> > > > > HJR

> > > > >

> > > > > "Eric Levinson" <nospam_at_nospam.com> wrote in message

> > > > > news:DjUI8.4416$3w2.19388_at_typhoon.sonic.net...

> > > > > > When a VARCHAR2 type column is defined, how does the LENGTH

> function

> > > get

> > > > > the

> > > > > > length of the varchar contained in the column?  Does it count up

> the

> > > > > number

> > > > > > of bytes to some end of string marker, or is there an internally

> > held

> > > > and

> > > > > > maintained attribute of varchar which maintains the size?

> > > > > >

> > > > > > Reason why I am asking, there might be a performance hit to use

> > LENGTH

> > > > if

> > > > > it

> > > > > > has to calculate it every time.

> > > > > >

> > > > > > Any help would be appreciated

> > > > > >

> > > > > > oracle at levinsong dot com

> > > > > >

> > > > > >

> > > > >

> > > > >

> > > >

> > > >

> > >

> > >

> >

> >

>

>