Entity Framework T-Sql “having” Equivalent

问题

How can I write a linq to entities query that includes a having clause?

For example:

SELECT State.Name, Count(*) FROM State
INNER JOIN StateOwner ON State.StateID = StateOwner.StateID
GROUP BY State.StateID
HAVING Count(*) > 1

回答1:

Any reason not to just use a where clause on the result?

var query = from state in states
            join stateowner in stateowners
              on state.stateid equals stateowner.stateid
            group state.Name by state.stateid into grouped
            where grouped.Count() > 1
            select new { Name = grouped.Key, grouped.Count() };

回答2:

I believe you can use a GroupBy followed by a Where clause and it will translate it as a Having. Not entirely sure though.

回答3:

If you want to compare a variable that is not in the group by (Ex: age), then it would be:

var duplicated = (
                  from q1 in db.table1
                  where (q1.age >= 10 )
                  group q1 by new { q1.firstName, q1.lastName } into grp
                  where (grp.Count() > 1 )
                  select new 
                   {
                     firstName= grp.Key.firstName,
                     lastName = grp.Key.lastName,
                   }
                 );

来源：https://stackoverflow.com/questions/1406962/entity-framework-t-sql-having-equivalent