I have a document like this:
{
"_id" : "4mDYgt6gID",
...
"MultipleChoiceQuestions" : [
{
...
"LeadInFile" : null,
...
},
{
...
"LeadInFile" : 'some string',
...
}
],
...
}
How do I query for any documents that have a non-null value in LeadInFile?
I'm trying different things, currently something like this
db.getCollection('QuizTime:Quizzes').find({"MultipleChoiceQuestions": [{ "LeadInFile": { $ne: null}}]});
Is returning 0 records.
The current form of the query is saying:
Find documents where MultipleChoiceQuestions is [{ "LeadInFile": { $ne: null}}]
Try using dot notation; this is used to access elements of an array or fields in an embedded document. For example:
db.getCollection('QuizTime:Quizzes').find({
"MultipleChoiceQuestions.LeadinFile" : { "$ne" : null }
})
Related
I have a JSON in MongoDB and I am trying to check if at least one of the items in the JSON doesn't contain a specific field.
{
"_id" : 12345,
"orderItems" : [
{
"itemId" : 45678,
"isAvailable" : true,
"isEligible" " false
},
{
"itemId" : 87653,
"isAvailable" : true
}
]
}
So in the above JSON, since the 2nd one under order items doesn't contain iseligible field, I need to get this _id.
I tried the below query so far, which didnt work:
db.getCollection('orders').find({"orderItems.iseligible":{$exists:false})
You can use $elemMatch to evaluate the presence of the nested key. Once that's accomplished, project out the _id value.
db.orders.find({
orderItems: {
$elemMatch: {
"isEligible": {
$exists: false
}
}
}
},
{
_id: 1
})
Here is a Mongo playground with the finished code, and a similar SO answer.
I have an old list of products that store the descriptions in an array at index [0]. The model is set up as a string. So my plan is to extract that value and add it to a temporary field. Step 2 would be to take that value and copy it to the original field.
This is the 'wrong' product I want to fix.
{_id : 1 , pDescription : ['great product']},
{_id : 2 , pDescription : ['another product']}
All I want to is to change the array to a string like this:
{_id : 1 , pDescription : 'great product'},
{_id : 2 , pDescription : 'another product'}
I have tried this to create the temporary description:
Products.aggregate([
{
$match: {
pDescription: {
$type: "array"
}
}
},
{
$set: {
pDescTemp: {
$first: "$pDescription"
}
}
}
]).exec((err, r) => {
// do stuff here
});
The command works fine without the $first command.
The error reads: MongoError: Unrecognized expression '$first'
Any tips on how to fix this are appreciated!
Thanks!
I believe this is what you need to update your pDescription field to be equal to the first element of the array already stored as pDescription:
db.Products.updateMany({},
[
{
$set: {
pDescription: {
$arrayElemAt: [
"$pDescription",
0
]
}
}
}
])
I have a user model like this:
user : {
myArmy : {
mySoldiers : [
{
positioned : false,
soldierInfo : {
_id : s99212
}
},
{
positioned : true,
soldierInfo : {
_id : s99112
}
}
]
}
},
user : {
myArmy : {
mySoldiers : [
{
positioned : true,
soldierInfo : {
_id : s99212
}
},
{
positioned : false,
soldierInfo : {
_id : s99112
}
}
]
}
}
...
I have a query that i want to do to return the user(s) who have soldier id s99212 positioned (true): (could be thousands of those, and i need to read and retrieve them all)
This is my faulty query with mongoose:
var soldierId = s99212;
stream = User.find({
$and: [
{'myArmy.mySoldier.positioned': {$ne: null}},
{'myArmy.mySoldier.soldierInfo._id': soldierId}
]
}).lean(true).stream();
Nothing is returned by this query, should there be another way to do this $and stuff?
How exactly am i suppose to use $elemMatch if at all, should it be instead of the find? (If it worth to mention, i want to return the complete user object, not just parts of it...)
Tried this, crashed my app:
stream = User.find({
'$elemMatch': [
{'myArmy.mySoldiers.pos': {$ne: null}},
{'myArmy.mySoldiers.soldierInfo._id': soldierId}
]
}).lean(true).stream();
I know i have a small syntax problem, where is it?
Very simple and well documented. The $elemMatch operator acts as a "query in itself", where it applies "it's conditions" to members of the array specified:
var query = User.find({
"myArmy.mySoldiers": {
"$elemMatch": {
"positioned": { "$ne": null },
"soldierInfo._id": soldierId
}
}
});
Therefore for a document to "match" then the conditions specfied under $elemMatch must be present and valid for the "same" array element. Array on "left", arguments on "right".
Other "dot notation" forms only ever test that the values match "some element" in the array, and not necessarily the same one.
In my mongodb (using Mongoose), I have story collection which has comments sub collection and I want to query the subdocument by client id, as
Story.find({ 'comments.client': id }, { title: 1, 'comments.$': 1 }, function (err, stories) {
...
})
})
The query works except that it only returns the first matched subdocument, but I want it to return all matching subdocuments. Did I miss an option?
EDIT:
On Blakes Seven's tip, I tried the answers from Retrieve only the queried element in an object array in MongoDB collection, but I couldn't make it work.
First tried this:
Story.find({'comments.client': id}, { title: 1, comments: {$elemMatch: { client: id } } }, function (err, stories) {
})
It also returns the first match only.
Then, I tried the accepted answer there:
Story.aggregate({$match: {'comments.client': id} }, {$unwind: '$comments'}, {$match : {'comments.client': id} }, function (err, stories) {
})
but this returns nothing. What is wrong here?
UPDATE:
My data structure looks like this:
{
"_id" : ObjectId("55e2185288fee5a433ceabf5"),
"title" : "test",
"comments" : [
{
"_id" : ObjectId("55e2184e88fee5a433ceaaf5"),
"client" : ObjectId("55e218446033de4e7db3f2a4"),
"time" : ISODate("2015-08-29T20:16:00.000Z")
}
]
}
In mongo I store object that have field "titleComposite". This field contains array of title object, like this:
"titleComposite": [
"0": {
"titleType": "01",
"titleText": "Test cover uploading"
}
]
I'm perfoming query and I would like to receive only "titleText" value for the returned values. Here is an example of my query:
db.onix_feed.find({"addedBy":201, "mediaFileComposite":{$exists:false}}, {"isbn13":1,"titleComposite.titleText":1})
In the results I see values like
{
"_id" : ObjectId("559ab286fa4634f309826385"),
"titleComposite" : [ { "titleText" : "The Nonprofit World" } ],
"isbn13" : "9781565495296"
}
Is there any way to get rid of "titleComposite" wrapper object and receive only titleText? For example, take titleText of the first element only?
Would appreciate any help
You can mongodb aggregation to achieve your expected result. Re-arrange your query as following...
db.onix_feed.aggregate([
{
$match: {
$and: [
{"addedBy":201},
{"mediaFileComposite":{$exists:false}}
]
}
},
{
$project : { titleText: "$titleComposite.titleText",
"isbn13" : 1 }
}
])