Question

I have the following scenario which can solved on the database level or the Linq to EF level:
Here is my view in the database:

id  title   date           weight
==================================
1   t1     2013-01-18       1.5
1   t1     2013-01-17       1.4
1   t1     2013-01-15       1.31
1   t1     2013-01-12       1.22
2   t2     2013-01-19       2.3
2   t2     2013-01-16       2.1
2   t2     2013-01-07       1.81
2   t2     2013-01-19       1.62

What I need as a result is one record from each item (t1 and t2) which is the newest one by date.

So the output will be like this:

id  title   date           weight
==================================
1   t1     2013-01-18       1.5
2   t2     2013-01-19       2.3

As I said above Answers on the database level or the linq level using (Distinct) are both welcomed.

Part of my c# linq:

mylist = (from a in db.myview
join art in db.viewTags on a.id equals art.ArticleID
where (art.TagID == tag.ID)
select a).Distinct().Take(10).ToList();

I need distinct records from myview according to a.id (id field of the view)

Thanks

Answer 1

EDIT – as per update you want distinct by id

Full article : DistinctBy in Linq (Find Distinct object by Property)

Following is part of MoreLINQ library.

Use DistinctBy function

public static IEnumerable<TSource> DistinctBy<TSource, TKey>
    (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
    HashSet<TKey> seenKeys = new HashSet<TKey>();
    foreach (TSource element in source)
    {
        if (seenKeys.Add(keySelector(element)))
        {
            yield return element;
        }
    }
}

So to find the distinct values using just the Id property, you could use:

mylist = (from a in db.myview
 join art in db.viewTags on a.id equals art.ArticleID
 where (art.TagID == tag.ID)
 select a).DistinctBy(a=>a.Id).Take(10).ToList();

---

select * from table 
inner join
(select max(date) as date,id from table group by id) d 
on d.id = table.id and d.date= table.date