Question

I have this SQL query

select at.description, 
       a.Address1, 
       a.Address2, 
       a.City
  from address_types at
  left join Address a
    on a.addresstype = at.addresstype
    and a.addressid=24

Would like to write it in Linq Lambda Expression, any clue?

Thanks!

Answer 1

I would rather simplify it in following way

(from at in address_types
join a in address 
on at.addresstype  equals a.addresstype  into tt
from ar in tt.DefaultIfEmpty()
where (ar != null && ar.addressid == 24)
select new 
 {
    at.Description,
    ar.Address1, 
    ar.Address2, 
    ar.City 
  })

The reason why we don’t need this check “(ja == null)” is because we already restricted our set in this line “where (ar != null && ar.addressid == 24)”.

Meanwhile this query works, my POV is that LEFT JOIN is also redundant here in the SQL query. You will not get NULL rows due to your condition “a.addressid = 24” so SQL can be rewritten to INNER JOIN and LINQ query as well to

(from at in address_types
    join a in address 
    on at.addresstype  equals a.addresstype
    where at.addressid == 24
    select new 
     {
        at.Description,
        a.Address1, 
        a.Address2, 
        a.City  
      })