MongoDB:通过多个条件查询嵌套数组

Question

假设这是我的用户收藏中的一项:

  {
    "_id" : "5545f4c4d0dd52c355a99fbe",
    "name" : "Dollie James",
    "device" : "iOS",
    "gender" : "Female",
    "wallet" : [
        {
            "store" : "All Saints",
            "balance" : "$196.11",
            "date" : "2014-02-22T22:09:38 -10:00",
            "tags" : [
                "Tshirt",
                "Summer"
            ]
        },
        {
            "store" : "Nike",
            "balance" : "$367.76",
            "date" : "2014-04-18T14:44:30 -10:00",
            "tags" : [
                "Shoes"
            ]
        }
    ]
}

此记录是从以下查询返回的:

db.users.findOne({$and:[{"wallet.tags": "Tshirt"}, {"wallet.store":"Nike"}]})

但这不是我想要的结果，因为 Tshirt 和 Nike 在 wallet 数组中不在同一个对象中。似乎 mongo 正在对整个数组进行查询。我如何定位此查询以仅返回数组中同一对象中的两个条件？

Answer 1

您不需要$and(因为它将独立应用条件)但是$elemMatch .来自文档:

The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.

在您的具体情况下:

> db.wallet.find(
              {wallet: { $elemMatch:{"tags" : "Tshirt", "store":"Nike"}}}
  ).pretty()
{
    "_id" : "5545f4c4d0dd52c355a99f00",
    "name" : "Working example",
    "device" : "iOS",
    "gender" : "Female",
    "wallet" : [
        {
            "store" : "Nike",
            "balance" : "$196.11",
            "date" : "2014-02-22T22:09:38 -10:00",
            "tags" : [
                "Tshirt",
                "Summer"
            ]
        }
    ]
}