用多个数组连接两个表的mongodb

Question

我有一张桌子会员，另一张是宣传代码。

成员资格表：

/* 1 */
{
    "_id" : ObjectId("5b62e7050b13587e9febb8db"),
    "country_id" : "5a093507f1d45633844096ef",
    "type" : "Bronze",
    "price" : "30",
}
/* 2 */
{
    "_id" : ObjectId("5b6961175140b477032291b7"),
    "country_id" : "5a093507f1d45633844096ef",
    "type" : "Gold",
    "price" : "1000",
}....

代码表:

{
    "_id" : ObjectId("5cfe23fd075be65883f6d921"),
    "final_status" : 1,
    "membership" : [ 
        ObjectId("5b62e7050b13587e9febb8db"), 
        ObjectId("5b6961175140b477032291b7"), 
        ObjectId("5b6961285140b477032291b8"), 
        ObjectId("5b7567dd5b874856981b53d3"), 
        ObjectId("5bba1c3794c6761db256edbc")
    ],
    "month" : [ 
        "1", 
        "3"
    ]
}

在这里，promomcode表有一个成员id。我想要有会员资格的广告代码数据，加入query.get，有会员资格的代码数据，请帮我

Answer 1

在mongodb中左外连接使用$lookup

​

db.promocode.aggregate([{
  $lookup: {
    from: 'membership',
    localField: 'membership',
    foreignField: '_id',
    as: 'memberships'
  }
}, {
  $project: {
    membership: 0
  }
}])

​