Mongoose .select() 方法的使用

Question

I'm pretty confused with the use of the select method. This is how I use it, and it's wrong:

Transaction.find({username : user.username}).select('uniqueId', 'confirmation_link', 'item_name', 'timeout', 'username', function(err, txs){
        callback(txs);
});

What I'm trying to achieve is simply to select from the transactions in the database the ones with that username and I want to take out just the fields listed in the select method. Can anyone point out how should I use the select method? Thanks.

Answer 1

the docs say you can achieve this like so:

Mongoose v4.0

// Retrieving only certain fields

Model.find({}, 'first last', function (err, docs) {

});

old outdated API

// Retrieving only certain fields

Model.find({}, ['first', 'last'], function (err, docs) {
  // docs is an array of partially-`init`d documents
  // defaults are still applied and will be "populated"
});

so you can do this without select() .

Answer 2

this is another way: queries in mongoose

Transaction.find({username : user.username})
.select('uniqueId confirmation_link item_name timeout username')
.exec(function(err, txs) {
        console.log(txs);
});

Answer 3

Now there is a shorter way of doing this (not using .select and not using an array), just passing the fields separate by spaces as the second argument

User.find({}, 'first last', function (err, usr) {
    //Got the result, saved a few bytes of code
});

The Docs

Answer 4

Select method is used to select which fields are to be returned in the query result, excluding select means we want all the other fields to be returned, here is simple usage as per the docs.

// include a and b, exclude other fields  
query.select('a b');

// exclude c and d, include other fields  
query.select('-c -d');

More information here, https://mongoosejs.com/docs/api.html#query_Query-select

Answer 5

要检索某些字段而不检索“_id”，您可以指定排除它

Model.find({}, {'Username':1, '_id':0}, function ( err, docs ){}.....

Answer 6

This was pretty helpful: How to protect the password field in Mongoose/MongoDB so it won't return in a query when I populate collections?

Looks like you have a few options.

1) Use select('-_id') . 2) Use find({whatever: values}, '-_id', callback...} . I can't verify this method, but if it works with select() , I don't see why it wouldn't work here.

Answer 7

To retrieve specific fields only, use the following,

Model.find({/*Your query*/}, {'firstName':1, 'lastname':1, '_id':0}, //Notice, this will omit _id! function ( err, docs ){}.....

that will work and will NOT bring in any extra id such as _id.

Answer 8

selection & projection operation can be done in this way easyly in nodejs. Try this

    var Selection={
        <some key of data model > : <target value for that key field>,
        <some key of data model > : <target value for that key field>
        //you can add many parameters here selection operation
        };
    var Projection = {
        __v    : false,
        _id    : false
        //you can add many parameters here for projection
    };
    <DataModel>.find(Selection,Projection,function (err,data) {
        if(err){
            console.log(err);
        }else{
         console.log(data);
        }
    });

Answer 9

这种语法也适用

Transaction.find({username : user.username}).select(['uniqueId', 'confirmation_link', 'item_name', 'timeout', 'username']);

Answer 10

Remove the commas and quotes between the fields you want to select:

Transaction.find({username : user.username}).select('uniqueId confirmation_link item_name timeout username', function(err, txs){
    callback(txs);
});

Answer 11

set select: false for the fields that you want to exclude in your Schema on server request.

example

const userSchema = mongoose.Schema({
    name: {
        type: String,
        select: false
    },

    password: {
        type: Number,
        select: false

    }
})

that way the only fields that you want coming in should be the ones without select: false

If for some reason you need to get the password(any field) but need to have select: false in the schema. use select('+password etc')