I have a query such as:
select something from somewhere join stuff on condition join more_stuff on condition where somewhere.sometime is null and somewhere.someone is null and stuff.whatever is null
and so on.
I try nonclustered group indexing
somewhere.someone, the query slows down. I read somewhere that MSSQL keeps a bitmap of nulls for each row.
The question is, how to speed up the query so that access to rows with the specified
null values is faster and indexed? (so you only scan rows with the specified
nulls, not full table scan) Can I somehow take advantage of this
null bitmap ?