Consider the following sample document
[{
"Name" : "John doe",
"age" : 22,
"email" : "john#doe.com"
},
{
"Name" : "William",
"age" : 28,
"email" : "william#william.com"
},
{
"Name" : "jack",
"age" : 22,
"email" : "jack#jack.com"
}]
I have an array of objects with me with the following structure
[{'name':'jack','age':10},{'name':'john','age':20}]
How do I perform a query in the document in a way such that I can match the name field and age field of my array of objects of each element.
Basically, the name jack and the age 10 should query with the sample and after that the name john and the age 20 should perform the query.
I know that $elemMatch could have been used if it was the other way around where I had to query with single elements in an array. Is there any way of doing this?
If you are not talking about searching the retrieved documents. You can search database like this:
var searchArr = [{name:'jack',age:10},{name:'john', age:20}]
searchArr.forEach(function(element){
var query = Model.find(element)
query.then(function(result){
console.log(result)
})
})
Related
I have two collections. The first collection contains students:
{ "_id" : ObjectId("51780f796ec4051a536015cf"), "name" : "John" }
{ "_id" : ObjectId("51780f796ec4051a536015d0"), "name" : "Sam" }
{ "_id" : ObjectId("51780f796ec4051a536015d1"), "name" : "Chris" }
{ "_id" : ObjectId("51780f796ec4051a536015d2"), "name" : "Joe" }
The second collection contains courses:
{
"_id" : ObjectId("51780fb5c9c41825e3e21fc4"),
"name" : "CS 101",
"students" : [
ObjectId("51780f796ec4051a536015cf"),
ObjectId("51780f796ec4051a536015d0"),
ObjectId("51780f796ec4051a536015d2")
]
}
{
"_id" : ObjectId("51780fb5c9c41825e3e21fc5"),
"name" : "Literature",
"students" : [
ObjectId("51780f796ec4051a536015d0"),
ObjectId("51780f796ec4051a536015d0"),
ObjectId("51780f796ec4051a536015d2")
]
}
{
"_id" : ObjectId("51780fb5c9c41825e3e21fc6"),
"name" : "Physics",
"students" : [
ObjectId("51780f796ec4051a536015cf"),
ObjectId("51780f796ec4051a536015d0")
]
}
Each course document contains students array which has a list of students registered for the course. When a student views a course on a web page he needs to see if he has already registered for the course or not. In order to do that, when the courses collection gets queried on the student's behalf, we need to find out if students array already contains the student's ObjectId. Is there a way to specify in the projection of a find query to retrieve student ObjectId from students array only if it is there?
I tried to see if I could $elemMatch operator but it is geared towards an array of sub-documents. I understand that I could use aggregation framework but it seems that it would be on overkill in this case. Aggregation framework would probably not be as fast as a single find query. Is there a way to query course collection to so that the returned document could be in a form similar to this?
{
"_id" : ObjectId("51780fb5c9c41825e3e21fc4"),
"name" : "CS 101",
"students" : [
ObjectId("51780f796ec4051a536015d0"),
]
}
[edit based on this now being possible in recent versions]
[Updated Answer] You can query the following way to get back the name of class and the student id only if they are already enrolled.
db.student.find({},
{_id:0, name:1, students:{$elemMatch:{$eq:ObjectId("51780f796ec4051a536015cf")}}})
and you will get back what you expected:
{ "name" : "CS 101", "students" : [ ObjectId("51780f796ec4051a536015cf") ] }
{ "name" : "Literature" }
{ "name" : "Physics", "students" : [ ObjectId("51780f796ec4051a536015cf") ] }
[Original Answer] It's not possible to do what you want to do currently. This is unfortunate because you would be able to do this if the student was stored in the array as an object. In fact, I'm a little surprised you are using just ObjectId() as that will always require you to look up the students if you want to display a list of students enrolled in a particular course (look up list of Id's first then look up names in the students collection - two queries instead of one!)
If you were storing (as an example) an Id and name in the course array like this:
{
"_id" : ObjectId("51780fb5c9c41825e3e21fc6"),
"name" : "Physics",
"students" : [
{id: ObjectId("51780f796ec4051a536015cf"), name: "John"},
{id: ObjectId("51780f796ec4051a536015d0"), name: "Sam"}
]
}
Your query then would simply be:
db.course.find( { },
{ students :
{ $elemMatch :
{ id : ObjectId("51780f796ec4051a536015d0"),
name : "Sam"
}
}
}
);
If that student was only enrolled in CS 101 you'd get back:
{ "name" : "Literature" }
{ "name" : "Physics" }
{
"name" : "CS 101",
"students" : [
{
"id" : ObjectId("51780f796ec4051a536015cf"),
"name" : "John"
}
]
}
It seems like the $in operator would serve your purposes just fine.
You could do something like this (pseudo-query):
if (db.courses.find({"students" : {"$in" : [studentId]}, "course" : courseId }).count() > 0) {
// student is enrolled in class
}
Alternatively, you could remove the "course" : courseId clause and get back a set of all classes the student is enrolled in.
I am trying to explain by putting problem statement and solution to it. I hope it will help
Problem Statement:
Find all the published products, whose name like ABC Product or PQR Product, and price should be less than 15/-
Solution:
Below are the conditions that need to be taken care of
Product price should be less than 15
Product name should be either ABC Product or PQR Product
Product should be in published state.
Below is the statement that applies above criterion to create query and fetch data.
$elements = $collection->find(
Array(
[price] => Array( [$lt] => 15 ),
[$or] => Array(
[0]=>Array(
[product_name]=>Array(
[$in]=>Array(
[0] => ABC Product,
[1]=> PQR Product
)
)
)
),
[state]=>Published
)
);
I'm creating an api with node.js, express and mongoose. I'm pretty new to mongosse and I am wondering if there exists a better way to do what I want.
I have two collections: users and expenses.
User example:
{
"_id" : ObjectId("59c4bc6a39d9992d6407427e"),
"firstName" : "John",
"lastName" : "Doe",
"name" : "JohnD",
"password" : "xxxxx",
"__v" : 26,
"budget" : 400,
"saving" : 300,
"wage" : 1340,
"expenses" : [
ObjectId("59cd076544fa3e64ec32c7e3"),
ObjectId("59cd07f0ed7bd2192cab72bd"),
ObjectId("59cd0a78e19060451059dce7"),
ObjectId("59cd0b24e19060451059dce8"),
ObjectId("59cd0b8fe19060451059dce9"),
ObjectId("59cdf34be19060451059dcf4"),
ObjectId("59cdf3c1e19060451059dcf5"),
ObjectId("59cdf417e19060451059dcf6"),
ObjectId("59cdf446e19060451059dcf7"),
ObjectId("59cdf46ee19060451059dcf8"),
ObjectId("59cdf4bce19060451059dcf9"),
ObjectId("59cdf6dee19060451059dcfa"),
ObjectId("59cdf6f5e19060451059dcfb"),
ObjectId("59cdf768e19060451059dcfc"),
ObjectId("59cdf798e19060451059dcfd"),
ObjectId("59cdf806e19060451059dcfe")
]
}
Expense example:
{
"_id" : ObjectId("59cd07f0ed7bd2192cab72bd"),
"name" : "shopping",
"price" : 100,
"date" : 1506607687013,
"repetition" : 0,
"__v" : 0
}
{
"_id" : ObjectId("59cd0a78e19060451059dce7"),
"name" : "gazoil",
"price" : 50,
"date" : 1506607687013,
"repetition" : 0,
"__v" : 0
}
I want to do a function which takes a user and return all of its expenses. Am I forced to loop through all objectId in user.expenses or there is a proper way to do that directly with mongoose ?
Mongoose has a method for doing what you are willing to do: Query Population
You need to set your schema right and push the refs to the children, then use the populate() method:
const user = await User
.findOne({ _id: 'yourObjId' })
.populate('expenses')
.exec()
console.log(user.stories)
You can use $lookup/aggregate
Check some examples on this answer which seem to explain your use case.
Mongodb, aggregate query with $lookup
I'm new to robmongo and I received an assignment to write some queries.
let say I have a collection that each key has some values for example value of "userId" and value of "deviceModel".
I need to write a query that shows for each device model how many users has this device.
this is what I got so far:
db.device_data.aggregate([ {"$group" : {_id:"$data.deviceModel", count:{$sum:1}}}])
The problem is that this aggregate for each device the number of keys it appears.
{
"_id" : { "$binary" : "AN6GmE7Thi+Sd/dpLRjIilgsV/4AAAg=", "$type" : "00" },
"auditVersion" : "1.0",
"currentTime" : NumberLong(1479301118381),
"data" : {
"deviceDesign" : "bullhead",
"loginType" : "GOOGLE",
"source" : "SDKLoader",
"systemUptimeMillis" : 137652880.0,
"simCountryIso" : "il",
"networkOperatorName" : "Cellcom",
"hasPhonePermission" : true,
"deviceIdentifier" : "353627074839559",
"sdkVersion" : "0.7.939.2016-11-14.masterDev",
"brand" : "google",
"osVersion" : "7.0",
"osVersionIncremental" : "3239497",
"deviceModel" : "Nexus 5X",
"deviceSDKVersion" : 24.0,
"manufacturer" : "LGE",
"sdkShortBuildDate" : "2016-11-14",
"sdkFullBuildDate" : "Mon Nov 14 22:16:40 IST 2016",
"product" : "bullhead"
},
"timezone" : "Asia/Jerusalem",
"collectionAlias" : "DEVICE_DATA",
"shortDate" : 17121,
"userId" : "00DE86984ED3862F9277F7692D18C88A#1927cc81cfcf7a467e9d4f4ac7a1534b"}
this is an example of how one key locks like.
The below query should give you distinct count of userId for a deviceModel. I meant if a same userId present for a deviceModel multiple items, it will be counted only once.
db.collection.aggregate([ {"$group" : {_id:"$data.deviceModel", userIds:{$addToSet: "$userId"}}
},
{
$unwind:"$userIds"
},
{
$group: { _id: "$_id", userIdCount: { $sum:1} }
}])
Unwind:-
Deconstructs an array field from the input documents to output a
document for each element.
In the above solution, it deconstructs the userId array formed on the first pipeline.
addToSet:-
Returns an array of all unique values that results from applying an
expression to each document in a group of documents that share the
same group by key.
This function ensures that only unique values are added to an array. In the above case, the userId is added to an array in the first pipeline.
When I try to find specific object in array using find({query}) I always get all elements from array.
Activities array stores activities (it would be a thousands of them) as you can see in the following snippet:
This is my collection:
{
"_id" : ObjectId("58407140755324d04db2ce95"),
"owner" : 103429326776572,
"activities" : [
{
"name" : "test1",
"startTime" : ISODate("2016-08-11T17:41:54Z"),
"type" : "te1",
"lat" : 1,
"lon" : 1,
"creator" : 126212904493088,
"coverPhoto" : {
"name" : "test1",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\SJ9tpP6Mx.jpg"
},
"identifier" : "H1g9F6vpGl",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
},
{
"name" : "test2",
"startTime" : ISODate("2016-08-11T17:41:53Z"),
"type" : "te2",
"lat" : 1,
"lon" : 1,
"creator" : 103312904493090,
"coverPhoto" : {
"name" : "test2",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\Hy8qpvafe.jpg"
},
"identifier" : "rJlU5TvpMx",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
}
]
}
I need to get for example an activity that has specific identifier.
I tried to use queries like:
1) db.myCollection.find({'activities.identifier' : "rJlU5TvpMx"})
2) db.myCollection.find({'activities' : { $elemMatch : { "identifier" : "rJlU5TvpMx", "creator" : 103312904493090 } })
And all combinations with '' or "" signs
I found above queries at mongodb docs in equal documents schema as mine is.
Can you tell me what am I doing wrong ?
You can try either use single match or multiple match based on your need. This makes use of $elemMatch(projection)
db.myCollection.find({"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: { identifier: "rJlU5TvpMx"}}})
db.myCollection.find( {"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: {creator : 103312904493090, identifier: "rJlU5TvpMx" }}})
You are looking for the projection object which gets passed as an argument in your query. It allows the return of specific fields from your search rather than the entire document. http://mongoosejs.com/docs/api.html#model_Model.find
I would also suggest looking at the response to this question here: Mongoose Query: Find an element inside an array which makes use of the unwind operator to enter the array as it seems to be relevant to your needs.
In the collection you are searching in, you have just one Document(Object). If you apply method find() to your collection and the query inside matches the value in activities.identifier it will return the only Document(object).
To have a better understanding of what I am talking about check example on mongoose API doc
And query result here.
Try check this out https://docs.mongodb.com/v3.0/reference/operator/projection/elemMatch/#proj._S_elemMatch instead
If my markup looks like this:
<div data-test="{ "value" : "bar", "_id" : 1234, "name" : "john", "age" : 25 }">...</div>
<div data-test="{ "value" : "foo", "_id" : 1235, "name" : "paul", "age" : 26 }">...</div>
<div data-test="{ "value" : "drummer", "_id" : 1236, "name" : "ringo", "age" : 22 }">...</div>
How would I select a particular element using JQuery if I only had the key 'bar' or 'foo'?
I could pull out the whole object for each row and iterate through it looking for a match but I'd rather not if there is a more efficient method.
How can I cleanly select based on the property of an object?
Try this
$('div[data-test$=": bar }"]')
$('div[data-test$=": foo }"]')
More details here
UPDATE:
If attributes are not ending with bar/foo then you could try contains selector
$('div[data-test*="'value' : 'bar'"]')
$('div[data-test*="'value': 'foo'"]')
More details here
Or you could also use starts selector if it starts with value
You can use:
$("div").filter(function() {
return $(this).data("test").value == "bar";
})
jQuery.data() automatically parses a data value that's in JSON format into the corresponding object.
FIDDLE