title: linq to sql query cannot be translated error
body: <p>Here is the query:</p>
  
  <pre><code>children = (from r in masterDB.mrrel_Limited2s
                              join s in masterDB.mrconso_SnoMed2014_LimitedToDiseaseBranches on r.AUI2 equals s.AUI                            
                              join a in masterDB.tbl_patients_problems_problemId_to_SnoMed_Iteration2_before_doc_final_s on s.SCUI equals a.SnoMedScui into aGroup
                              from aa in aGroup.DefaultIfEmpty()
                              join g in masterDB.tbl_patients_problems_to_snomed_groups_2014s on s.SCUI equals g.SnoMedScui into gGroup
                              from gg in gGroup.DefaultIfEmpty()
                              where r.AUI1.Equals(node.Value.Split(new string[] { " @ " }, StringSplitOptions.RemoveEmptyEntries)[0])
                              &amp;&amp;
                              r.REL.Equals("CHD")
                              select new RadTreeNode(
                                  s.AUI + " @ " + s.SCUI + " @ " + aa != null &amp;&amp; gg == null ? "1" : "0" + " @ "
                                  + gg != null ? gg.GroupName : "0" + " @ " + s.SCUI,
                                  s.STR
                                  )).ToList();
  </code></pre>
  
  <p>I am trying to join two tables where a couple of conditions are met (two where clauses at the bottom) and then left join that set on two more tables. I am getting a "cannot translate query" run time error. All advice is appreciated. Thanks in advance.</p>