Help explain this linq query and how can it be improved?

Question

Can this linq query be made more concise and improved? And can someone explain the original as well as an refactored version:

Owners.GroupJoin (OwnerSubs, 
                  tl => tl.Unq, 
                  j => j.Unq, 
                  (tl, tl_j) => new  
              {
                  tl = tl, 
                  tl_j = tl_j
              }
                  )
                  .Where (temp0 => (temp0.tl.Id == "123"))
                  .SelectMany (temp0 => temp0.tl_j.DefaultIfEmpty (), 
                          (temp0, j) => new  
                      {
                      Id = temp0.tl.Id, 
                      Business = temp0.tl.Business, 
                      Unq = j.Unq
                      }
                  )

Also, this pulls back a bunch of duplicates unless I add a Distinct()? Is there way to avoid using the Distinct?