I'm trying to use a projection parameter on findOne() to extract a single field from a document (stats) but it just seems to return the whole document. I'm using version "mongodb": "^3.4.1" in Node.js
This is the document structure
{ _id: 5e563015fa9a1a0134cac3cb,
username: 'user1',
password: '1234',
email: 'user@email.com',
stats:
{ totalViewed: 122,
totalUnique: 4,
tknow: 80,
tdknow: 42,
setCnt: 78 },
progress:
[ { cardId: 1001, knowCnt: 3, dknowCnt: 4 },
{ cardId: 1016, knowCnt: 0, dknowCnt: 0 } ] }
This is the code:
var findOneDoc = function() {
db.collection("testusers").findOne(
{ username: "user1" },
{ stats: 1 }, //field to return
function(err, result) {
if (err) {
console.log("Error: ", err);
}
console.log("Success: ", result);
}
);
};
findOneDoc();
I also tried: {$project: {stats: 1}}
, to no avail
Thanks
Based on the documentation the .findOne()
method takes options as a second parameter and it is recommended to use projection
to define fields:
db.collection("testusers").findOne(
{ username: "user1" },
{ projection: { stats: 1 } },
function(err, result) { ... }
);
with findOne
operations, the second parameter passed is an options parameter, so you should pass in your projects within the options parameter, like this:
query = { username: "user1" };
options = { projection: { stats: 1 }};
db.collection("testusers").findOne(query, options)
findOne returns a document. use find() …..
you can do it like mick said, with findOne
await db.collection("testusers").findOne(
{ username: "user1" },
{ projection: { stats: 1 } },
function(err, result) { ... }
);
or you can do it with find, like that
await db.collection("testusers")
.find({ username: "user1" })
.limit(1)
.project(["stats"])
.toArray()
you can add fields to the array project for more fields
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