从子文档返回字段数组

Question

任何人都可以帮助我查询mongo以释放数组，我使用的是mongdb本机驱动程序我的收集文档如下，也请忽略我的objectId它只是示例

{  
      "_id":ObjectId(123),
      "name":"Sam",
      "age":20,
      "hobbiesDetail":[  
         {  
            "description":"FootBall",
            "level":"20%"
         },
         {  
            "description":"Cricket",
            "level":"80%"
         }
      ]
   },
   {  
      "_id":ObjectId(124),
      "name":"Ted",
      "age":26,
      "hobbiesDetail":[  
         {  
            "description":"FootBall",
            "level":"20%"
         }
      ]
   }

而我的预期产出是

[  
   {  
      "name":"Sam",
      "age":20,
      "hobbies":"Football,Cricket"
   },
   {  
      "name":"Ted",
      "age":26,
      "hobbies":"Football"
   }
]

我只想解开我的数组，在一个查询中的爱好描述之间添加一个逗号，谢谢你的帮助

Answer 1

您所需要的只是一个带有数组操作符的$项目。

db.collection.aggregate([
    { "$project": { 
        "name": 1, 
        "age": 1, 
        "hobbies": { 
            "$map": { 
                "input": "$hobbiesDetail", 
                "as": "hobby", 
                "in": "$$hobby.description" 
            } 
        } 
    }}
])