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To remove an array element, simply use $pull along with update(). Let us create a collection with documents −> db.demo146.insertOne({"ListOfEmployeeNames":["Chris", "David", "Bob", "Mike"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f54ffdf09dd6d08539bd") }Display all documents from a collection with the help of find() method −> db.demo146.find();This will produce the following output −{ "_id" : ObjectId("5e32f54ffdf09dd6d08539bd"), "ListOfEmployeeNames" : [ "Chris", "David", "Bob", "Mike" ] }Following is the query to remove an array element from MongoDB −> db.demo146.update({}, { "$pull": { "ListOfEmployeeNames": "Bob" } }); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Display all documents from a collection with ... Read More
For writing an equality, you can simply use find() along with match value. Let us create a collection with documents −> db.demo145.insertOne({"ListOfNames":["Chris", "David", "Mike"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f37bfdf09dd6d08539bb") } > db.demo145.insertOne({"ListOfNames":["Bob", "John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f384fdf09dd6d08539bc") }Display all documents from a collection with the help of find() method −> db.demo145.find();This will produce the following output −{ "_id" : ObjectId("5e32f37bfdf09dd6d08539bb"), "ListOfNames" : [ "Chris", "David", "Mike" ] } { "_id" : ObjectId("5e32f384fdf09dd6d08539bc"), "ListOfNames" : [ "Bob", "John" ] }Following is the query to implement MongoDB operator $eq −> db.demo145.find({"ListOfNames":"John"});This will produce ... Read More
Let us first create a collection with documents −>db.demo144.insertOne({"EmployeeDetails":[{"EmployeeName":"Chris", "EmployeeEmail":"Chris12@gmail.com"}, {"EmployeeName":"Bob", "EmployeeEmail":"bo22@gmail.com"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f1d8fdf09dd6d08539b9") } >db.demo144.insertOne({"EmployeeDetails":[{"EmployeeName":"David", "EmployeeEmail":"david@gmail.com"}, {"EmployeeName":"Carol", "EmployeeEmail":"Carol@gmail.com"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f1f5fdf09dd6d08539ba") }Display all documents from a collection with the help of find() method −> db.demo144.find();This will produce the following output −{ "_id" : ObjectId("5e32f1d8fdf09dd6d08539b9"), "EmployeeDetails" : [ { "EmployeeName" : "Chris", "EmployeeEmail" : "Chris12@gmail.com" }, { "EmployeeName" : "Bob", "EmployeeEmail" : "bo22@gmail.com" } ] } { "_id" : ObjectId("5e32f1f5fdf09dd6d08539ba"), "EmployeeDetails" : [ { "EmployeeName" ... Read More
StackWalker API is a new feature in Java 9, and it improves the performance of the predecessor stack track element. It can also provide a way to filter the stack elements in case of exception or to understand application behavior. In Java 9, the way to access the stack trace is very limited and provide the entire stack information at once.In the below example, we need to print all attributes in Stack Frame Exampleimport java.lang.StackWalker.StackFrame; import java.util.*; import java.util.stream.*; import java.lang.StackWalker.Option; public class AllAttributesTest { public static void main(String args[]) { System.out.println("Java 9 Stack Walker API - Print all ... Read More
For this, simply use update() to update. Let us create a collection with documents −> db.dem0143.insertOne({"StudentId":1, "Details":{"Name":"Chris"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e32eb9efdf09dd6d08539b7") } > db.dem0143.insertOne({"StudentId":2, "Details":{"Name":"David"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e32eba5fdf09dd6d08539b8") }Display all documents from a collection with the help of find() method −> db.dem0143.find();This will produce the following output −{ "_id" : ObjectId("5e32eb9efdf09dd6d08539b7"), "StudentId" : 1, "Details" : { "Name" : "Chris" } } { "_id" : ObjectId("5e32eba5fdf09dd6d08539b8"), "StudentId" : 2, "Details" : { "Name" : "David" } }Following is the query to implement $set and $push in a single update ... Read More
For this, you can use aggregate(). Let us create a collection with documents −> db.demo142.insertOne({"Value":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e32e9c6fdf09dd6d08539b2") } > db.demo142.insertOne({"Value":45}); { "acknowledged" : true, "insertedId" : ObjectId("5e32e9cafdf09dd6d08539b3") } > db.demo142.insertOne({"Value":60}); { "acknowledged" : true, "insertedId" : ObjectId("5e32e9cdfdf09dd6d08539b4") } > db.demo142.insertOne({"Value":55}); { "acknowledged" : true, "insertedId" : ObjectId("5e32e9d0fdf09dd6d08539b5") } > db.demo142.insertOne({"Value":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e32e9d9fdf09dd6d08539b6") }Display all documents from a collection with the help of find() method −> db.demo142.find();This will produce the following output −{ "_id" : ObjectId("5e32e9c6fdf09dd6d08539b2"), "Value" : 50 } { ... Read More
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 More
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 More
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 More
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 More