Mongoose find documents if array contains a value

问题

so i have this schema

const Document = new mongoose.Schema({
    _id:{
        type:Number
    },
    creationDate:{
    type:Date,
    default:Date.now(),
    },
    title:String,
    status:{
        type:String,
        default:status.PENDING
    },
    description: String,
    category:[{
        type:mongoose.Schema.Types.ObjectId,
        ref:'Categories',
    }],
})

how do i find documents that their category array contains an id given ? i mean like a query to get all documents using category id

回答1:

There are some ways to achieve this. First one is by $elemMatch operator:

const docs = await Documents.find({category: { $elemMatch: {$eq: 'yourCategory'} }});
// you may need to convert 'yourCategory' to ObjectId

Second one is by $in or $all operators:

const docs = await Documents.find({category: { $in: [yourCategory] }});

const docs = await Documents.find({category: { $all: [yourCategory] }});
// you can give more categories with these two approaches 
//and again you may need to convert yourCategory to ObjectId

$in is like OR and $all like AND. For further details check this link : https://docs.mongodb.com/manual/reference/operator/query/all/

Third one is by aggregate() function:

const docs = await Documents.aggregate([
    { $unwind: '$category' },
    { $match: { 'category': mongoose.Schema.Types.ObjectId(yourCategory) } }
]};

with aggregate() you get only one category id in your category array.

回答2:

I believe a simple find query would do.

Document.find({'category._id': 'id'}, function (err, docs) {});

Document.find({'category._id': 'id'})
.then(docs => {
    console.log(docs)
})
.catch(error => {
    console.log(error)
})

When you use reference then you can get elements by their ids with _id.

Now you may notice that you will only see the id itself. To actually see what is in the category, you will need to use populate.

Document.find({
  'category._id': 'id'
}).populate({
    path: 'category'
}).exec((err, doc) => {
  if (!err) {
    console.log(doc)
  } else {
    console.log(err)
  }
})

来源：https://stackoverflow.com/questions/63368225/mongoose-find-documents-if-array-contains-a-value

标签

node.js

mongodb

mongoose