Re: index

"Evan Keel" <evankeel_at_sbcglobal.net> wrote in message news:dbrjk.6804$cn7.4273_at_flpi145.ffdc.sbc.com...
>
> "Brian Selzer" <brian_at_selzer-software.com> wrote in message
> news:%Vpjk.34162$ZE5.24396_at_nlpi061.nbdc.sbc.com...
>>
>> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
>> news:488de63f$0$4041$9a566e8b_at_news.aliant.net...
>> > aarklon_at_gmail.com wrote:
>> >
>> >> Hi all,
>> >>
>> >> I read the following in a book
>> >>
>> >> 1) we can have several non clustered indexes on a table , but we can
>> >> have only one clustered index per table
>> >>
>> >> 2) index on the primary key can be clustered or non clustered
>> >>
>> >> now my question is
>> >>
>> >> 1) to what extent these statements are true ?
>> >
>> > To the extent the statements accurately describe the physical
>> > implementation of a particular dbms, they are true.
>> >
>> > Theoretically, one can have multiple clustered indexes at the cost of
>> > duplicating the data, which of course incurs a cost. Vendors typically
>> > assUme nobody would ever want to incur that cost.
>>
>> This is bunk. Badour is an idiot. Where there is a clustered index,
>> that
>> index /is/ the table--that is, the table is physically stored using
> whatever
>> data structure is in use for indexes--probably b-trees. A table that
>> does
>> not have a clustered index, on the other hand, is physically stored as a
>> heap. The leaf nodes of a clustered index /are/ the rows of the table.
> The
>> leaf nodes of a non-clustered index are either pointers to rows on the
> heap
>> (where there is no clustered index) or clustered index keys (along with a
>> uniquifier [I didn't coin the term, so don't blame me] if the clustered
>> index isn't also a unique index). Although it is possible to have
> multiple
>> indexes that cover the entire heading, that is not the same thing as
> having
>> multiple clustered indexes.
>>
> Though I agree with you, you are not a very nice person. Why the invective
> re: Badour?
>

Badour has frequently used that term (among others) to describe me, and I've already turned the other cheek--more than once, I might add. Even though I know it isn't very Christian, I have progressed past the "You don't cast pearls after swine." stage to the point that I can't help but illuminate every flaw in anything he posts. Bottom line: he earned that invective, and I am more than happy to pay. Received on Tue Jul 29 2008 - 02:09:18 CEST