Question

Could somebody assist me in converting a sql query into LINQ, i’m pretty handy with linq but this is a bit much and i can’t download linqpad here!

select 
    t.*, 
    l.*
from
    email_templates t 
left join 
    (select
        id as email_id,
        sent_at,
        sent_by
    from 
        email_log 
    where 
        id = (select max(id)
              from email_log
              where as_at_date = '20100618'
              group by template_id  ) 
    )l 
on t.id = v.template_id

Answer 1

By the way I understand your query; you need something like this…

var maxId = (from e in email_log
             where e.as_at_date < new DateTime(2010, 06, 18)
             group e by e.template_id into grouped
             select grouped.Max(a => a.id)).First();

var selectedEmailLog = from e in email_log
                       where e.id == maxId
                       select new
                       {
                           email_id = e.id,
                           e.sent_at,
                           e.sent_by,
                           e.template_id,
                       };

var seletedRows = from t in email_templates
                  join l in selectedEmailLog 
                    on t.id equals l.template_id into tls
                  from tl in tls
                  select new
                  {
                      t.id,
                      tl.email_id,
                      tl.sent_at,
                      tl.sent_by,
                  };

… LINQ is composable so you can break your query into manageable parts. Breaking your query into smaller parts will make it much easier to understand. You can also return complex objects instead of creating flat record rendering from your database.