SQL查詢LINQ如何在LINQ

Question

select * 
from impact 
where (usedin&1)=1 
and impactid not in 
    (select impactid 
    from responsetime 
    where scontractid= scontractid ) 

我學習LINQ查詢寫。 我想在LINQ中寫這個查詢。

Answer 1

有人告訴我，像這樣的SQL查詢會更快。

select * 
from impact i 
left outer join responsetime r on i.impactid = r.impactid 
where (usedin&1)=1 
    and scontractid= scontractid 
    and r.impact is null 

轉換，爲LINQ，我們得到：

from i in impact 
from r in responsetime.Where(rr=>i.impactid = rr.impactid).DefaultIfEmpty() 
where (i.usedin&1)=1 
    and i.scontractid= scontractid 
    and r.impact is null 
select i