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.sometime
and 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 ?