Re: Performance question

I have actually answered this already. The "n" is what gets stored with the row, so there is no overhead in processing that field. The row says "next 5 characters is surname", "SMITH". Even though the field is defined as varchar2(10). In your terminology, that means the "n" is the actual bytecount per row.

As for where the varchar2(10) gets stored, where do we store anything about the definition of a table? In the data dictionary.

HJR "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
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>
Received on Wed May 29 2002 - 16:58:00 CDT