MongoDB操作符中的$elemMatch问题

问题 如果MongoDB 数据库集合中仅存在一条记录 { "_id" : ObjectId("5e6b4ef546b5f44e5c5b276d"), "name" : "赵小明", "used_name" : [ "赵明", "赵小朋" ], "age" : 16, "gender" : 0, "relatives" : [ { "name" : "赵刚", "relationship" : 0 }, { "name" : "秀英", "relationship" : 1