Question

有人可以协助我将SQL查询转换为LINQ，我对linq非常方便，但这有点多了，我不能在这里下载linqpad！

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

顺便说一句，我理解你的查询;你需要这样的东西......

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是可组合的，因此您可以将查询分解为可管理的部分。将查询分解为更小的部分将使其更容易理解。您还可以返回复杂对象，而不是从数据库创建平面记录呈现。

帮助sql进行linq转换

1 个答案: