Question

我有三个集合，其中包含如下所示的数据，

客户集合

{ 
    "_id" : ObjectId("5a058e316803fafd127b23c9"), 
    "client_name" : "client A", 
    "client_status" : "A"
}
{ 
    "_id" : ObjectId("5a058e316803fafd127b23cb"), 
    "client_name" : "client B", 
    "client_status" : "A"
}

泳池收藏

{ 
    "_id" : ObjectId("5a0e76f66803fa530a7b23d4"), 
    "pool_name" : "pool A", 
    "pool_status" : "A", 
    "client_id" : ObjectId("5a058e316803fafd127b23c9"), 
    "schools" : [
        ObjectId("5a0e742b6803faa6097b2462"), 
        ObjectId("5a0e742b6803faa6097b2464")
    ]
}
{ 
    "_id" : ObjectId("5a0e76f76803fa530a7b2402"), 
    "pool_name" : "pool B", 
    "pool_status" : "A", 
    "client_id" : ObjectId("5a058e316803fafd127b23c9"), 
    "schools" : [
        ObjectId("5a0e742b6803faa6097b2463")
    ]
}
{ 
    "_id" : ObjectId("5a0e76f76803fa530a7b23f6"), 
    "pool_name" : "pool C", 
    "pool_status" : "A", 
    "client_id" : ObjectId("5a058e316803fafd127b23cb"), 
    "schools" : [
        ObjectId("5a7aa1476803fa1f117b23d1")
    ]
}

学校收藏

{ 
    "_id" : ObjectId("5a0e742b6803faa6097b2462"), 
    "school_name" : "School A", 
    "school_status" : "A"
}
{ 
    "_id" : ObjectId("5a0e742b6803faa6097b2463"), 
    "school_name" : "School B", 
    "school_status" : "A"
}
{ 
    "_id" : ObjectId("5a0e742b6803faa6097b2464"), 
    "school_name" : "School C", 
    "school_status" : "A"
}
{ 
    "_id" : ObjectId("5a7aa1476803fa1f117b23d1"), 
    "school_name" : "School D", 
    "school_status" : "A"
}

从这个集合中，我需要为波纹管这样的客户获取泳池学校的列表。

**Output**

{
    "_id" : ObjectId("5a058e316803fafd127b23c9"),
    "client_name" : "client A", 
    "client_status" : "A"
    "pools" : [
        {
            "_id" : ObjectId("5a0e76f66803fa530a7b23d4"), 
            "pool_name" : "pool A", 
            "pool_status" : "A",
            'schools' => [
                { 
                    "_id" : ObjectId("5a0e742b6803faa6097b2462"), 
                    "school_name" : "School A", 
                    "school_status" : "A"
                },
                { 
                    "_id" : ObjectId("5a0e742b6803faa6097b2464"), 
                    "school_name" : "School C", 
                    "school_status" : "A"
                },
            ]
        },
        {
            "_id" : ObjectId("5a0e76f76803fa530a7b2402"), 
            "pool_name" : "pool B", 
            "pool_status" : "A",
            "schools" : [
                { 
                    "_id" : ObjectId("5a0e742b6803faa6097b2463"), 
                    "school_name" : "School B", 
                    "school_status" : "A"
                }   
            ]
        }
    ]
},
{
    "_id" : ObjectId("5a058e316803fafd127b23cb"), 
    "client_name" : "client B",
    "client_status" : "A"
    "pools" : [
        {
            "_id" : ObjectId("5a0e76f76803fa530a7b23f6"), 
            "pool_name" : "pool C", 
            "pool_status" : "A",
            "schools" : [
                { 
                    "_id" : ObjectId("5a7aa1476803fa1f117b23d1"), 
                    "school_name" : "School D", 
                    "school_status" : "A"
                }
            ]
        }
    ]
}

Answer 1

您可以尝试以下汇总

Mongodb 3.6引入了嵌套$lookup管道...因此，您无需像上面那样使用另一个$lookup阶段...您可以使用嵌套$lookup管道这里

Client.aggregate([
  { "$match": { 'client_status': 'A' } },
  { "$lookup": {
    "from": Pool.collection.name,
    "let": { "client_id": "$_id" },
    "pipeline": [
      { "$match": { "$expr": { "$eq": [ "$client_id", "$$client_id" ] } } },
      { "$addFields": {
        "schools": {
          "$ifNull": ["$schools", []]
        }
      }}
      { "$lookup": {
        "from": Schools.collection.name,
        "let": { "schools": "$schools" },
        "pipeline": [
          { "$match": { "$expr": { "$in": [ "$_id", "$$schools" ] } } }
        ],
        "as": "schools"
      }}
    ],
    "as": "pools"
  }}
])

有关冗长的解释，您可以浏览$lookup multiple levels without $unwind?

从mongodb中的三个集合中获取结果

1 个答案: