英文:
How to project a list of a specific field from a nested list of objects?
问题
这是样本文档：
{_id: ObjectId("60a8f82df06d8601849b2a01"),pokemon: [{"id": 1,"num": 1,"name": "bulbasaur","img": "img.com","type": ["grass", "poison"],"height": 112,"weight": 33},{"id": 2,"num": 2,"name": "char","img": "img.com","type": ["grass", "poison"],"height": 112,"weight": 33}]}
我想要从这个列表中提取名称。
这是我的代码：
const client = new MongoClient(url);console.log("connected")await client.connect();const db = client.db('cluster0');const collection = db.collection('testing');let datas = await collection.find({'pokemon.0.name': "bulbasaur"}).toArray();console.log(datas)
尝试了不同的查询操作符，如文本匹配，但仍然不起作用。
英文:
I have mongodb documents, each contains a pokemon array, where each item is an object. This is a sample document:
{_id: ObjectId("60a8f82df06d8601849b2a01")pokemon: [{"id": 1,"num": 1,"name": "bulbasaur","img": "img.com","type": ["grass", "poison"],"height": 112,"weight": 33},{"id": 2,"num": 2,"name": "char","img": "img.com","type": ["grass", "poison"],"height": 112,"weight": 33}]}
I want to extract the names from this list.
This is my code
const client = new MongoClient(url);console.log("connected")await client.connect();const db = client.db('cluster0');const collection = db.collection('testing');let datas = await collection.find({'pokemon.0': {name: "bulbasaur"}}).toArray();console.log(datas)
Tried different query operators such as text matching but still not working
答案1
得分: 1
如果你想查找一个其第一个宝可梦的名字是"bulbasaur"的文档，请尝试：
let data = await collection.find({"pokemon.0.name": "bulbasaur"})
如果你只想返回宝可梦的名字，你可以使用投影：
let data = await collection.findOne({"pokemon.0.name": "bulbasaur"},{_id: 0, names: {$map: {input: "$pokemon", in: "$$this.name"}}})console.log(data.names)
英文:
If you want to find a document which its first pokemon's name is "bulbasaur", try:
let data = await collection.find({"pokemon.0.name": "bulbasaur"})
And if you want to return only the pokemon names, you can use projection:
let data = await collection.findOne({"pokemon.0.name": "bulbasaur"},{_id: 0, names: {$map: {input: "$pokemon", in: "$$this.name"}}})console.log(data.names)
See how it works on the playground example
答案2
得分: 1
如果你特别想要只获取那个对象，那么使用这个：
db.collection.find({"pokemon.name": "Bulbasaur"},{"pokemon.$": 1})
英文:
If you want particularly that object only then use this
db.collection.find({"pokemon.name": "Bulbasaur"},{"pokemon.$": 1})
答案3
得分: 0
如果您想使位置动态，并仍然搜索“bulbasaur”，您可以使用：
db.collection.find({"pokemon": {"$elemMatch": {name: "bulbasaur"}}})
您可以在此处阅读更多信息 => 查询嵌入式文档数组
您还可以在 playground 上进行测试。
英文:
If you want position to be dynamic and still search for "bulbasaur" you can use:
db.collection.find({"pokemon": {"$elemMatch": {name: "bulbasaur"}}})
You can read more about it here =>
Query an Array of Embedded Documents
You can also test it on playground
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