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Database Articles
Page 235 of 546
Using count equivalent in MongoDB to find top users with max occurrence
To get the count and top users, use $group along with aggregate() . Let us create a collection with documents −> db.demo264.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed441627c0c63e7dba9e") } > db.demo264.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed471627c0c63e7dba9f") } > db.demo264.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed491627c0c63e7dbaa0") } > db.demo264.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed4c1627c0c63e7dbaa1") } > db.demo264.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed4e1627c0c63e7dbaa2") } > db.demo264.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ed531627c0c63e7dbaa3") }Display all documents from a collection with the help ...
Read MoreMongoDB query to skip documents
To skip documents in MongoDB, use skip(). Let us create a collection with documents −> db.demo263.insertOne({_id:100}); { "acknowledged" : true, "insertedId" : 100 } > db.demo263.insertOne({_id:200}); { "acknowledged" : true, "insertedId" : 200 } > db.demo263.insertOne({_id:300}); { "acknowledged" : true, "insertedId" : 300 }Display all documents from a collection with the help of find() method −> db.demo263.find();This will produce the following output −{ "_id" : 100 } { "_id" : 200 } { "_id" : 300 }Following is the query to skip document −> result = db.demo263.aggregate([ ... { ... $project: { ... v_id: { $ifNull: [null, [100, 200]] } ... ... } ... }, ... { $unwind: '$v_id' }, ... { $sort: { v_id: 1, _id: 1 } }, ... ... { $skip: 2 }, ... { $limit: 2 } ...]);This will produce the following output −{ "_id" : 300, "v_id" : 100 } { "_id" : 100, "v_id" : 200 }
Read MoreInvert Result of MongoDB Query (Implement Opposite of $and operation)?
To invert result i.e. opposite of $and operation, use $OR along with $ne. Let us first create a collection with documents −> db.demo4.insert({uid:1, "Name":"Chris", "Age":22}); WriteResult({ "nInserted" : 1 }) > db.demo4.insert({uid:2, "Name":"David", "Age":21}); WriteResult({ "nInserted" : 1 }) > db.demo4.insert({uid:3, "Name":"Bob", "Age":23}); WriteResult({ "nInserted" : 1 }) > db.demo4.insert({uid:1, "Name":"Carol", "Age":20}); WriteResult({ "nInserted" : 1 })Following is the query to display all documents from a collection with the help of find() method −> db.demo4.find();This will produce the following output −{ "_id" : ObjectId("5e0a1da125ddae1f53b62221"), "uid" : 1, "Name" : "Chris", "Age" : 22 } { "_id" : ObjectId("5e0a1db025ddae1f53b62222"), "uid" : ...
Read MoreModify sequence in MongoDB
To modify a sequence, use findAndModify(). Let us create a collection with documents −> db.demo261.insertOne({_id:100, Name:"Chris"}); { "acknowledged" : true, "insertedId" : 100 }Display all documents from a collection with the help of find() method −> db.demo261.find();This will produce the following output −{ "_id" : 100, "Name" : "Chris" }Following is the query to modify sequence −> db.demo262.insert({_id:"newId", sequence_value:0}) WriteResult({ "nInserted" : 1 }) > function getNext(sName){ ... ... var d= db.demo262.findAndModify({ ... query:{_id: sName}, ... update: {$inc:{sequence_value:1}}, ... new:true ... }); ... return d.sequence_value; ...}Following is the query to call ...
Read MoreInvoke convertToCapped and convert an existing collection to capped in MongoDB
To convert an existing collection to capped, use convertToCapped. Let us create a collection with documents −> db.demo260.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47b1181627c0c63e7dba9b") } > db.demo260.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47b11c1627c0c63e7dba9c") } > db.demo260.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47b11f1627c0c63e7dba9d") }Display all documents from a collection with the help of find() method −> db.demo260.find();This will produce the following output −{ "_id" : ObjectId("5e47b1181627c0c63e7dba9b"), "Name" : "Chris" } { "_id" : ObjectId("5e47b11c1627c0c63e7dba9c"), "Name" : "Bob" } { "_id" : ObjectId("5e47b11f1627c0c63e7dba9d"), "Name" : "David" }Following is the query to invoke convertToCapped ...
Read MoreGet MongoDB documents that contains specific attributes in array
For this, you can use $and along with dot(.) notation. Let us first create a collection with documents −>db.demo2.insertOne({"StudentInformation":[{"StudentName":"John", "StudentAge":21}, {"StudentName":"Mike", "StudentAge":22}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e08b56e25ddae1f53b62219") } >db.demo2.insertOne({"StudentInformation":[{"StudentName":"Carol", "StudentAge":19}, {"StudentName":"Bob", "StudentAge":18}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e08b58625ddae1f53b6221a") }Following is the query to display all documents from a collection with the help of find() method −> db.demo2.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e08b56e25ddae1f53b62219"), "StudentInformation" : [ { "StudentName" : "John", "StudentAge" : 21 }, ...
Read MoreHow to run MongoDB shell using mongos command?\\n
In order to launch the MongoDB shell, you need to use mongo command. Following is the syntax −>mongoFirst reach the MongoDB bin directory from command prompt as in the below screenshot −Here is the command to launch the mongo shell as in the below screenshot −This will produce the following output −
Read MoreHow to update % printed to Console from MongoDB?
To update and print to console from MongoDB script, create a variable and then use the print() method.Let us first create a variable −> var amount=10.58945;Here is the query to update % printed to console −> var amount=10.58945; > print(amount.toFixed(2)+" %");This will produce the following output −10.59 %
Read MoreMongoDB inverse of query to return all items except specific documents?
To get documents except some specific documents, use $nor along with $and. Let us first create a collection with documents −> db.demo1.insertOne({"StudentName":"Chris", "StudentMarks":38}); { "acknowledged" : true, "insertedId" : ObjectId("5e08a4f025ddae1f53b62216") } > db.demo1.insertOne({"StudentName":"David", "StudentMarks":78}); { "acknowledged" : true, "insertedId" : ObjectId("5e08a4f725ddae1f53b62217") } > db.demo1.insertOne({"StudentName":"Mike", "StudentMarks":96}); { "acknowledged" : true, "insertedId" : ObjectId("5e08a4fd25ddae1f53b62218") }Following is the query to display all documents from a collection with the help of find() method −> db.demo1.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e08a4f025ddae1f53b62216"), "StudentName" : "Chris", "StudentMarks" : 38 } { "_id" : ...
Read MoreHow to specify the order in which the query returns matching documents in MongoDB
To specify the order in which the query returns matching documents, use cursor.sort() in MongoDB. The cursor is db.collectionName.find().Let us create a collection with documents −> db.demo259.insertOne({"Subject":"MySQL"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ae1f1627c0c63e7dba98") } > db.demo259.insertOne({"Subject":"Java"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ae231627c0c63e7dba99") } > db.demo259.insertOne({"Subject":"MongoDB"}); { "acknowledged" : true, "insertedId" : ObjectId("5e47ae281627c0c63e7dba9a") }Display all documents from a collection with the help of find() method −> db.demo259.find();This will produce the following output −{ "_id" : ObjectId("5e47ae1f1627c0c63e7dba98"), "Subject" : "MySQL" } { "_id" : ObjectId("5e47ae231627c0c63e7dba99"), "Subject" : "Java" } { "_id" : ObjectId("5e47ae281627c0c63e7dba9a"), "Subject" ...
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