请教个uniCloud二级分佣连表查询的问题

如题：

用户表：user，其中upcode记录的是该用户所属上级的ucode，如表中用户2和4为1的下级

{  
  "_id": 1,  
  "ucode": 111,  
  "uname": "张"  
}  
{  
  "_id": 2,  
  "ucode": 222,  
  "upcode": 111,  
  "uname": "王"  
}  
{  
  "_id": 3,  
  "ucode": 333,  
  "upcode": 222,  
  "uname": "李"  
}  
{  
  "_id: "4,  
  "ucode": 444,  
  "upcode": 111,  
  "uname": "赵"  
}

订单表：order

{  
  "_id": 1,  
  "ucode": 111,  
  "orderName": "商品1",  
  "orderPrice":24  
}  
{  
  "_id": 2,  
  "ucode": 222,  
  "orderName": "商品1",  
  "orderPrice":24  
}  
{  
  "_id": 3,  
  "ucode": 333,  
  "orderName": "商品1",  
  "orderPrice":24  
}  
{  
  "_id": 4,  
  "ucode": 444,  
  "orderName": "商品1",  
  "orderPrice":24  
}  
{  
  "_id": 5,  
  "ucode": 222,  
  "orderName": "商品1",  
  "orderPrice":24  
}

比如我是ucode为111的用户，现在想要把order表中是我下级用户（222和333）的订单返回来，要怎么实现呢？