linq to sql group by having

Question

Could any one show my how to write query using linq to sql to search for suburbs which have at least 1 venue in specific state

Location

SuburbID
SuburbName
StateName

Venue

VenueID
VenueName
SuburbName
StateName

Answer 1

var locations = from loc 
                in dataContext.Locations 
                where loc.Venues.Count > 1 
                select loc

EDIT: Final answer:

If you have the foreign keys setup between Location/Venue:

string stateName = "New York";  

var locations = from loc 
                in dataContext.Locations 
                where loc.Venues.Count > 1 && loc.StateName == stateName 
                select loc;

---

If there isn't a foreign key relationship:

string stateName = "New York";

var locations = (from v 
                 in dataContext.Venues 
                 where v.StateName == stateName 
                 select (from l 
                         in dataContext.Locations 
                         where l.SuburbName == v.SuburbName && l.StateName == v.Statename              
                         select l
                        ).Single()).Distinct();

---

Really though, you should fix your tables. The Venue table should have a suburbID instead of "StateName" and "SuburbName" - it is redundant to keep both.

Answer 2

Here's a couple of simple answers:

var suburbNames = dataContext.Venues
  .Where(v => v.StateName == specificState)
  .GroupBy(v => v.SuburbName)
  .Select(g => g.Key)

           //

var locations = dataContext.Location
  .Where(loc => loc.StateName == specificState)
  .Where(loc => loc.Venues.Any())

With that Venues property: you can get that by adding the relationship in the linq to sql designer - even if the foreign key doesn't exist / isn't enforced in the database.