NHibernate QueryOver: Get a row count with group by in a subquery

Question

I\'m trying to get a count from a query with a group by and just can\'t figure out how to translate the SQL I want into NHibernate\'s QueryOver syntax.

This is the SQL:<

Answer 1

I'm not sure why you need such a complex query. If you only want the count of distinct emails meeting certain criteria I think you could use something like this in SQL:

select count(distinct email)
from Entry
where (conditions...)

And translating this to NHibernate's QueryOver API would look something like this:

int count = session.QueryOver<ContestEntry>()
            .Select(Projections.CountDistinct<ContestEntry>(x => x.Email))
            .FutureValue<int>()
            .Value;//query is not executed until here

Unless I'm missing something, I think this will get the result you're after. There is also a "Distinct" projection and a .ToRowCountQuery() method that you might find interesting.