Update mongodb

Src/Asp.NetCore2/MongoDbTest/UnitTest/QueryLeftJoin.cs

@@ -64,6 +64,20 @@ namespace MongoDbTest
                     StudentName = x.Name,
                     SchoolName = y.Name
                 }).ToList();
+
+            if (list.Count != 3)  Cases.ThrowUnitError();
+            if (list.Any(s=>s.SchoolName== "TestSchool") ==false) Cases.ThrowUnitError();
+            if (list.Any(s => s.StudentName == "jack") == false) Cases.ThrowUnitError();
+
+            var list2 = db.Queryable<Student>()
+               .InnerJoin<School>((x, y) => x.SchoolId == y.Id)
+               .Select((x, y) => new
+               {
+                   StudentName = x.Name,
+                   SchoolName = y.Name
+               }).ToList(); 
+            if (list2.Count != 1) Cases.ThrowUnitError();
+            if (list2.Any(s => s.SchoolName == "TestSchool") == false) Cases.ThrowUnitError();
         }
         [SqlSugar.SugarTable("UnitStudent123131")]
         public class Student : MongoDbBase

Src/Asp.NetCore2/SqlSugar.MongoDbCore/MongoDb/SqlBuilder/MongoDbQueryBuilder.cs

@@ -215,11 +215,27 @@ namespace SqlSugar.MongoDb
                 operations.Add(lookupDoc.ToJson(UtilMethods.GetJsonWriterSettings()));
 
                 // $unwind
-                var unwindDoc = new BsonDocument("$unwind", new BsonDocument
+                BsonValue unwindDoc = null;
+                if (item.JoinType == JoinType.Left)
+                {
+                    unwindDoc=new BsonDocument("$unwind", new BsonDocument
                     {
                      { "path", $"${asName}" },
                        { "preserveNullAndEmptyArrays", true }
                     });
+                }
+                else if(item.JoinType==JoinType.Inner)
+                {
+                    // InnerJoin: 不保留空数组和null
+                    unwindDoc = new BsonDocument("$unwind", new BsonDocument
+                    {
+                        { "path", $"${asName}" }
+                    });
+                }
+                else 
+                {
+                    throw new Exception(" No Support "+item.JoinType);
+                }
                 operations.Add(unwindDoc.ToJson(UtilMethods.GetJsonWriterSettings()));
             }
         }