If I'm not mistaken a bitmap index also indexes null values. As far as I know, sqlserver does not have special indexes (not) considering specific null values. A regular index will work. Lookup Indexes in Books Online (BOL).
In the analyzer (turn on execution plan):
set nocount on
create table tab1 (myint integer null, myval integer not null)
create index idx_tab1_myint on tab1 (myint)
insert into tab1 (myint, myval) values (1,1)
insert into tab1 (myint, myval) values (null,2)
A bitmap index is an index that can be used on columns with little different values in it (eg sexe: values male, female and unknown/null), for example in Oracle. This type of index is not available in SQL Server.
Originally Posted by kaiowas
If I'm not mistaken a bitmap index also indexes null values.
In SQL Server you can also create indexes that allow null values