Question

I’ve been assigned a new project at work which uses NHibernate. A query that I can easily write in sql has me totally stumped on how to do it in linq, which is how I’ve been told to do it.

So, here’s the query:

select  ts.BatchID, COUNT(distinct ts.UniqID) SurveyCount
from    TeleformStaging.TeleformStaging ts
where   ts.IsRescan = 0
and     not exists (select  bfr.BatchID
                    from    TeleformStaging.BatchesForRescan bfr
                    where   bfr.BatchTrack = ts.BatchID)
group by ts.BatchID
order by ts.BatchID

I believe I could get the ‘group by’ portion, but no idea on the subquery.

Thanks for any advice…

Answer 1

Maybe something like this:

var result= (
        from ts in db.TeleformStaging
        where ts.IsRescan == false //if is a boolean else == 0
        && 
        !(
            from bfr in db.BatchesForRescan
            select bfr.BatchTrack
        ).Contains(ts.BatchID)
        orderby ts.BatchID
        group ts by ts.BatchID into g
        select new
        {
            BatchID=g.Key,
            SurveyCount=g.Select (x =>x.UniqID).Distinct().Count()
        }
    );

where db is the linq data context

Edit

You could also do it with .Any(). Like this:

var result= (
        from ts in db.TeleformStaging
        where ts.IsRescan == false //if is a boolean else == 0
        && 
        !(
            from bfr in db.BatchesForRescan
            where ts.BatchID==bfr.BatchTrack
            select bfr.BatchTrack
        ).Any()
        orderby ts.BatchID
        group ts by ts.BatchID into g
        select new
        {
            BatchID=g.Key,
            SurveyCount=g.Select (x =>x.UniqID).Distinct().Count()
        }
    );

Edit 1

Useful links:

• Contains
• Any
• Simple group by
• Basic LINQ Query Operations (C#)
• Order by