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Articles by AmitDiwan
Page 621 of 839
MongoDB query to get average in aggregation of array element?
To get an average of array elements, use $avg. Let us create a collection with documents −> db.demo584.insertOne({"Marks":[75,50,85,60,80]});{ "acknowledged" : true, "insertedId" : ObjectId("5e91d827fd2d90c177b5bcc2") }Display all documents from a collection with the help of find() method −> db.demo584.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e91d827fd2d90c177b5bcc2"), "Marks" : [ 75, 50, 85, 60, 80 ] }Following is the query to find avg in the aggregation of array element −> db.demo584.aggregate([ ... { $project: { MarksAvg: { $avg: "$Marks"} } } ... ])This will produce the following output −{ "_id" : ObjectId("5e91d827fd2d90c177b5bcc2"), "MarksAvg" : 70 }
Read MoreApply the Group Accumulator Operator $first on the system variable $$ROOT to return reference to the root document?
The accumulators are operators that maintain their state as documents progress through the pipeline.The $ROOT references the root document, i.e. the top-level document, currently being processed in the aggregation pipeline stage.Let us create a collection with documents −> db.demo582.insertOne({FirstName:"Chris", Age:21, createDate:new ISODate("2020-01-10")});{ "acknowledged" : true, "insertedId" : ObjectId("5e91ce41fd2d90c177b5bcbd") } > db.demo582.insertOne({FirstName:"Chris", Age:21, createDate:new ISODate("2020-04-21")});{ "acknowledged" : true, "insertedId" : ObjectId("5e91ce4ffd2d90c177b5bcbe") } > db.demo582.insertOne({FirstName:"Chris", Age:22, createDate:new ISODate("2020-02-11")});{ "acknowledged" : true, "insertedId" : ObjectId("5e91ce59fd2d90c177b5bcbf") } > db.demo582.insertOne({FirstName:"Chris", Age:22, createDate:new ISODate("2020-01-12")});{ "acknowledged" : true, "insertedId" : ObjectId("5e91ce6efd2d90c177b5bcc0") }Display all documents from a collection with the help of find() method ...
Read MoreHow do I order a list and add position to its items in MongoDB?
To order a list, use sort(). Let us create a collection with documents −> db.demo581.insertOne({"Name":"Chris", "Score":56});{ "acknowledged" : true, "insertedId" : ObjectId("5e91cbbbfd2d90c177b5bcb6") } > db.demo581.insertOne({"Name":"Bob", "Score":240});{ "acknowledged" : true, "insertedId" : ObjectId("5e91cbbbfd2d90c177b5bcb7") } > db.demo581.insertOne({"Name":"David", "Score":150});{ "acknowledged" : true, "insertedId" : ObjectId("5e91cbbcfd2d90c177b5bcb8") }Display all documents from a collection with the help of find() method −> db.demo581.find();This will produce the following output −{ "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb6"), "Name" : "Chris", "Score" : 56 } { "_id" : ObjectId("5e91cbbbfd2d90c177b5bcb7"), "Name" : "Bob", "Score" : 240 } { "_id" : ObjectId("5e91cbbcfd2d90c177b5bcb8"), "Name" : "David", "Score" : 150 }Following is the query ...
Read MoreSum unique properties in different collection elements in MongoDB and get the resultant Price?
To calculate the sum of unique properties in different collection elements, use $cond along with $group. This gives the resultant price.Let us create a collection with documents −> db.demo580.insertOne( ... { ... "Name":"John", ... "Id1":"110", ... "Id2":"111", ... "Price":10.5 ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e918cebfd2d90c177b5bcae") } > > db.demo580.insertOne( ... { ... "Name":"John", ... "Id1":"111", ... "Id2":"", ... "Price":9.5 ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e918cecfd2d90c177b5bcaf") }Display all documents ...
Read MoreMongoDB query to slice only one element of array
To slice only one element of array, use $slice in MongoDB. Let us create a collection with documents −> db.demo579.insertOne( ... { ... "_id" : 101, ... "details" : { "FirstName" : "John" }, ... "Marks" : [ 56,78,90,34,45,74 ] ... } ... ); { "acknowledged" : true, "insertedId" : 101 }Display all documents from a collection with the help of find() method −> db.demo579.find().pretty();This will produce the following output −{ "_id" : 101, "details" : { "FirstName" : "John" }, "Marks" : [ 56, 78, 90, 34, 45, 74 ] }Following is the query to slice only one the element of the array −> db.demo579.find({},{Marks : {$slice : 1} ,"details":0,"_id":0})This will produce the following output −{ "Marks" : [ 56 ] }
Read MoreMongoDB aggregation with equality inside array?
For this, use aggregate() along with $group. Let us create a collection with documents −> db.demo578.insertOne( ... { ... "_id" : 1, ... "Info" : { ... "firstName" : "Chris", ... "lastName" : "Brown" ... }, ... ... "achievements" : [ ... { ... "winner" : "10th", ... "year" : 2010, ... "by" : "School" ... ...
Read MoreSort MongoDB Collection by Array value?
To sort MongoDB collection by Array value, use aggregate() along with $sort. Let us create a collection with documents −> db.demo577.insertOne( ... { ... ... "student": { ... "details": [ ... { ... Name:"Chris", ... Score:45 ... }, ... { ... Name:"Bob", ... Score:33 ... ...
Read MoreSort and get only the first two fields in a “$group” operation in MongoDB
Let us create a collection with documents −> db.demo576.insertOne({id:101, Name:"Chris", Marks:45}){ "acknowledged" : true, "insertedId" : ObjectId("5e916c3b581e9acd78b427fa") } > db.demo576.insertOne({id:101, Name:"John", Marks:55}){ "acknowledged" : true, "insertedId" : ObjectId("5e916c43581e9acd78b427fb") } > db.demo576.insertOne({id:101, Name:"John", Marks:65}){ "acknowledged" : true, "insertedId" : ObjectId("5e916c47581e9acd78b427fc") } > db.demo576.insertOne({id:102, Name:"David", Marks:37}){ "acknowledged" : true, "insertedId" : ObjectId("5e916c55581e9acd78b427fd") } > db.demo576.insertOne({id:102, Name:"David", Marks:75}){ "acknowledged" : true, "insertedId" : ObjectId("5e916c5e581e9acd78b427fe") }Display all documents from a collection with the help of find() method −> db.demo576.find();This will produce the following output −{ "_id" : ObjectId("5e916c3b581e9acd78b427fa"), "id" : 101, "Name" : "Chris", "Marks" : 45 } { ...
Read MoreHide id field in MongoDB
Let us create a collection with documents −> db.demo575.insertOne({id:101, Information:{Name:"Chris", Age:21}});{ "acknowledged" : true, "insertedId" : ObjectId("5e916a55581e9acd78b427f7") } > db.demo575.insertOne({id:102, Information:{Name:"David", Age:20}});{ "acknowledged" : true, "insertedId" : ObjectId("5e916a5f581e9acd78b427f8") } > db.demo575.insertOne({id:101, Information:{Name:"Bob", Age:23}});{ "acknowledged" : true, "insertedId" : ObjectId("5e916a67581e9acd78b427f9") }Display all documents from a collection with the help of find() method −> db.demo575.find();This will produce the following output −{ "_id" : ObjectId("5e916a55581e9acd78b427f7"), "id" : 101, "Information" : { "Name" : "Chris", "Age" : 21 } } { "_id" : ObjectId("5e916a5f581e9acd78b427f8"), "id" : 102, "Information" : { "Name" : "David", "Age" : 20 } } { "_id" ...
Read MoreWorking with Aggregation to match all the values in MongoDB
To match all the values in MongoDB, use $match along with $and in Aggregation. Let us create a collection with documents −> db.demo574.insertOne( ... { ... "details1": { ... "details2": { ... "dueDate": new ISODate("2020-01-10"), ... "Name": "Chris", ... ... "UserInformation": { ... "Name": "John", ... "Marks": 78 ... }, ... ...
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