I never claimed that the clustered index will be on a different file group then the table. I do claim however that that when I create a clustered index, it doesn’t have to be created the same file group that the table already exists on. Of course when I create it on a different file group, the table will be transferred to the file group that the new clustered index will be created on. This means that sometime the clustered index will be created on the same file group as the table, but other times it will be created on a different file group and the table will be moved to this file group. Here is a small demo, that shows it:

--Creating a database with few file groups

CREATE DATABASE TestDB

ON

PRIMARY

(NAME = PrimaryFile,

FILENAME = 'c:\TestDB.mdf',

SIZE = 100MB),

FILEGROUP DefaultFileGroup

( NAME = DefaultFile,

FILENAME = 'c:\DefaultFile.ndf',

SIZE = 100MB)

LOG ON

(NAME = DemoDBLog,

FILENAME = 'c:\TestDB.ldf',

SIZE = 100MB)

go

use TestDB

go

-- Setting the default file group

ALTER DATABASE TestDB

MODIFY FILEGROUP DefaultFileGroup default

go

--Creating a demo table in the default file group

create table MyTable (i int not null) on DefaultFileGroup

go

--see that the table is created on the DefaultFileGroup

exec sp_help MyTable

--Adding a clustered index without speciying where it will be located

create clustered index cix_MyTable_i on MyTable (i) on [primary]

go

--The table is now on the primary data file and not on the default data file

sp_help MyTable

--cleanup

use master

go

drop database TestDB

Adi