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Database Articles
Page 233 of 546
MongoDB query to find last object in collection?
To find last object in collection, at first sort() to sort the values. Use limit() to get number of values i.e. if you want only the last object, then use limit(1).Let us first create a collection with documents −> db.demo141.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c347fdf09dd6d08539ae") } > db.demo141.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c34bfdf09dd6d08539af") } > db.demo141.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c34ffdf09dd6d08539b0") } > db.demo141.insertOne({"Name":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c352fdf09dd6d08539b1") }Display all documents from a collection with the help of find() method −> db.demo141.find();This will ...
Read MoreMongoDB: $nin and $in not working together in $elemMatch to fetch documents having subjects “MongoDB”, but not “Java”
For such kind of fetching, use only $nin and $in. Let us create a collection with documents −> db.demo140.insertOne({"Id":101, "Subjects":["MongoDB", "MySQL"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c149fdf09dd6d08539a9") } > db.demo140.insertOne({"Id":102, "Subjects":["MongoDB", "Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c14cfdf09dd6d08539aa") } > db.demo140.insertOne({"Id":103, "Subjects":["MongoDB", "PL/SQL"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c157fdf09dd6d08539ab") } > db.demo140.insertOne({"Id":104, "Subjects":["MongoDB", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c163fdf09dd6d08539ac") } > db.demo140.insertOne({"Id":105, "Subjects":["C", "C++"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31c16ffdf09dd6d08539ad") }Display all documents from a collection with the help of find() method −> ...
Read MoreHow to retrieve all nested fields from MongoDB collection?
For this, use aggregate(). Let us create a collection with documents −>db.demo138.insertOne({"Id":101, "PlayerDetails":[{"PlayerName":"Chris", "PlayerScore":400}, {"PlayerName":"David", "PlayerScore":1000}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31bb9ffdf09dd6d08539a1") } >db.demo138.insertOne({"Id":102, "PlayerDetails":[{"PlayerName":"Bob", "PlayerScore":500}, {"PlayerName":"Carol", "PlayerScore":600}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e31bbcefdf09dd6d08539a2") }Display all documents from a collection with the help of find() method −> db.demo138.find();This will produce the following output −{ "_id" : ObjectId("5e31bb9ffdf09dd6d08539a1"), "Id" : 101, "PlayerDetails" : [ { "PlayerName" : "Chris", "PlayerScore" : 400 }, { "PlayerName" : "David", "PlayerScore" : 1000 } ] } { "_id" : ObjectId("5e31bbcefdf09dd6d08539a2"), ...
Read MoreHow to compare two fields in aggregation filter with MongoDB?
For this, use aggregate() along with $filter. Let us create a collection with documents −> db.demo137.insertOne( ... { ... Name1:"Chris", ... Name2:"David", ... Detail1:[ ... {_id:"John", Name3:"Chris"}, ... {_id:"Chris", Name3:"Chris"}, ... ], ... Detail2:[{_id:"David", Name3:"Chris"}, ... {_id:"Carol", Name3:"Chris"}, ... {_id:"John", Name3:"Chris"}] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e31b4cefdf09dd6d08539a0") }Display all documents from a collection with the help of find() method −> db.demo137.find();This will ...
Read MoreHow to update array of subdocuments in MongoDB?
To update, use update() along with $set. Let us create a collection with documents −>db.demo134.insertOne({"EmployeeId":101, "EmployeeDetails":[{"EmployeeName":"Chris", "EmployeeAge":27}, {"EmployeeName":"Bob", "EmployeeAge":28}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e319b2f68e7f832db1a7f7c") } >db.demo134.insertOne({"EmployeeId":102, "EmployeeDetails":[{"EmployeeName":"David", "EmployeeAge":24}, {"EmployeeName":"Carol", "EmployeeAge":29}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e319b4468e7f832db1a7f7d") }Display all documents from a collection with the help of find() method −> db.demo134.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e319b2f68e7f832db1a7f7c"), "EmployeeId" : 101, "EmployeeDetails" : [ { "EmployeeName" : "Chris", "EmployeeAge" : 27 }, ...
Read MoreGroup by day/month/week based on the date range in MongoDB
To group, use $week and $month in MongoDB. Let us create a collection with documents −> db.demo133.insertOne({"Rank":18, "DueDate":new ISODate("2020-01-10")}); { "acknowledged" : true, "insertedId" : ObjectId("5e31980968e7f832db1a7f78") } > db.demo133.insertOne({"Rank":12, "DueDate":new ISODate("2020-01-10")}); { "acknowledged" : true, "insertedId" : ObjectId("5e31982568e7f832db1a7f79") } > db.demo133.insertOne({"Rank":12, "DueDate":new ISODate("2020-02-01")}); { "acknowledged" : true, "insertedId" : ObjectId("5e31986568e7f832db1a7f7a") } > db.demo133.insertOne({"Rank":20, "DueDate":new ISODate("2020-02-01")}); { "acknowledged" : true, "insertedId" : ObjectId("5e31986c68e7f832db1a7f7b") }Display all documents from a collection with the help of find() method −> db.demo133.find();This will produce the following output −{ "_id" : ObjectId("5e31980968e7f832db1a7f78"), "Rank" : 18, "DueDate" : ISODate("2020-01-10T00:00:00Z") } ...
Read MoreGroup across two columns in MongoDB?
To group across two columns, use $lookup. Let us create a collection with documents −> db.demo132.insertOne({"CountryName1":"US", "CountryName2":"UK", Value:50}); { "acknowledged" : true, "insertedId" : ObjectId("5e31950468e7f832db1a7f75") } > db.demo132.insertOne({"CountryName1":"UK", "CountryName2":"AUS", Value:10}); { "acknowledged" : true, "insertedId" : ObjectId("5e31951d68e7f832db1a7f76") } > db.demo132.insertOne({"CountryName1":"AUS", "CountryName2":"US", Value:40}); { "acknowledged" : true, "insertedId" : ObjectId("5e31952c68e7f832db1a7f77") }Display all documents from a collection with the help of find() method −> db.demo132.find();This will produce the following output −{ "_id" : ObjectId("5e31950468e7f832db1a7f75"), "CountryName1" : "US", "CountryName2" : "UK", "Value" : 50 } { "_id" : ObjectId("5e31951d68e7f832db1a7f76"), "CountryName1" : "UK", "CountryName2" : "AUS", "Value" : ...
Read MoreHow to query MongoDB a value with $lte, $in and $not to fetch specific values?
Let us first create a collection with documents −> db.demo130.insertOne( ... { ... ... "PlayerDetails":[{Score:56}, {Score:78}, {Score:89}, {Score:97}] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e3065bf68e7f832db1a7f6d") } > db.demo130.insertOne( ... { ... ... "PlayerDetails":[{Score:45}, {Score:56}] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e3065c068e7f832db1a7f6e") }Display all documents from a collection with the help of find() method −> db.demo130.find();This will produce the following output −{ "_id" : ObjectId("5e3065bf68e7f832db1a7f6d"), "PlayerDetails" : [ { "Score" : 56 }, { "Score" : 78 }, { "Score" : 89 }, ...
Read MoreGet distinct values from a column in MongoDB?
To get distinct values from a column, use distinct() in MongoDB. Let us first create a collection with documents −> db.demo128.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e30583d68e7f832db1a7f5d") } > db.demo128.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e30584068e7f832db1a7f5e") } > db.demo128.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e30584368e7f832db1a7f5f") } > db.demo128.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e30584668e7f832db1a7f60") } > db.demo128.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e30584c68e7f832db1a7f61") }Display all documents from a collection with the help of find() method −> db.demo128.find();This will produce the following output −{ "_id" : ...
Read MoreHow to add new item in nested array with MongoDB?
For this, use find() along with update(). Let us create a collection with documents −> db.demo124.insertOne( ... { ... "Name" : "John", ... "Id" : 101, ... "ProjectDetails" : [{ ... "ProjectName1" : "Online Book", ... "ProjectName2" : "Online Banking" ... }, { ... "ProjectName1" : "Online Library Management System", ... "ProjectName2" : "School Management System" ... }] ... } ... ); { "acknowledged" : true, "insertedId" ...
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