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Database Articles
Page 247 of 546
In MongoDB will limit() increase query speed?
No, using LIMIT() decreases the bandwidth consumption and it does not increase query speed. Let us see an example and create a collection with documents −> db.demo197.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afde803d395bdc21346d8") } > db.demo197.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdef03d395bdc21346d9") } > db.demo197.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf203d395bdc21346da") } > db.demo197.insertOne({"Name":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf603d395bdc21346db") } > db.demo197.insertOne({"Name":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf903d395bdc21346dc") } > db.demo197.insertOne({"Name":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afe1603d395bdc21346dd") } > db.demo197.insertOne({"Name":"John"}); { ...
Read MoreMongoDB query in object of arrays
Let us first create a collection with documents −> db.demo194.insertOne( ... { ... "_id": 101, ... "details": { ... "otherDetails": { ... "List1": ["MongoDB", "MySQL"], ... "List2": ["Java"], ... "List3": ["MongoDB", "C"] ... } ... } ... } ...); { "acknowledged" : true, "insertedId" : 101 } > db.demo194.insertOne( {"_id": 102, "details": { "otherDetails": { "List1": ["Java", "C"], "List2": ["C++"], "List3": ["Python", "Spring"] } } } ...
Read MoreHow to improve the execution time of a query in MongoDB?
To improve the execution time of a query, use index along with unique:true. Let us create a collection with documents −> db.demo193.createIndex({"LastName":1}, {unique:true}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo193.insertOne({"FirstName":"John", "LastName":"Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ade1803d395bdc21346d1") } > db.demo193.insertOne({"FirstName":"John", "LastName":"Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ade1f03d395bdc21346d2") } > db.demo193.insertOne({"FirstName":"David", "LastName":"Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ade2803d395bdc21346d3") }Display all documents from a collection with the help of find() method −> db.demo193.find();This will produce the following output −{ "_id" ...
Read MoreHow to get values of cursor in MongoDB?
To get values of cursor in MongoDB, use hasNext(). Let us create a collection with documents −> db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"Chris Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad95303d395bdc21346c5") } > db.demo191.insertOne({"EmployeeId":2, "EmployeeName":"David Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad95f03d395bdc21346c6") } > db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"John Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad96803d395bdc21346c7") } > db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"John Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad97003d395bdc21346c8") }Display all documents from a collection with the help of find() method −> db.demo191.find();This will produce the following output −{ "_id" : ObjectId("5e3ad95303d395bdc21346c5"), "EmployeeId" : 1, "EmployeeName" : "Chris ...
Read MoreMongoDB aggregation with multiple keys
To implement aggregation with multiple keys, use aggregate() along with $group. Let us create a collection with documents −> db.demo190.insertOne( ... { ... ... "DueDate" : ISODate("2020-01-01"), ... "Value" : 10, ... "Name" : "Chris" ... } ...); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad76403d395bdc21346bf") } > > db.demo190.insertOne( ... { ... ... "DueDate" : ISODate("2020-02-05"), ... "Value" : 30, ... "Name" : "David" ... } ...); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad76403d395bdc21346c0") } > db.demo190.insertOne( ... { ...
Read MoreMongoDB query to sort by the sum of specified object inside inner array?
To sort by the sum of specified object inside inner array, use $match along with $sort. Let us create a collection with documents −> db.demo189.insertOne( ... { ... "_id" : 100, ... "List" : [ ... { ... "Value" : 10 ... }, .. .{ ... "Value" : 20 ... }, ... { ... "Value" : 10 ... ...
Read MoreWhat kind of MongoDB query finds same value multiple times in an array?
To find same value multiple times, use $where in MongoDB. Let us create a collection with documents −> db.demo188.insertOne( ... { ... "ListOfData":[ ... {"Data": 100}, ... {"Data": 200}, ... {"Data": 100} ... ] ... } ...); { "acknowledged" : true, "insertedId" : ObjectId("5e3ad1c203d395bdc21346bd") } > db.demo188.insertOne( ... { ... "ListOfData":[ ... {"Data": 100}, ... {"Data": 200}, ... {"Data": 300} ... } ...); { ...
Read MoreFind in MongoDB documents with filled nested array and reshape the documents result
Let us first create a collection with documents −> db.demo187.insertOne( ... { ... "_id" : "101", ... "Details" : [ ... { "Subject" : "MongoDB" }, ... { "Subject" : "MySQL" } ... ] ... } ...); { "acknowledged" : true, "insertedId" : "101" } > db.demo187.insertOne( ... { ... "_id" : "102", ... "Details" : [ ... { } ... ] ... } ...); { "acknowledged" : true, "insertedId" : "102" ...
Read MoreMongoDB query to count the frequency of every element of the array
To count, you can also use aggregate() along with $sum. Let us create a collection with documents −> db.demo184.insertOne({"Names":["Chris", "David", "Bob"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e3999fb9e4f06af55199805") } > db.demo184.insertOne({"Names":["Chris", "Mike"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e399a0d9e4f06af55199806") } > db.demo184.insertOne({"Names":["Chris", "Bob", "Carol"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e399a209e4f06af55199807") }Display all documents from a collection with the help of find() method −> db.demo184.find();This will produce the following output −{ "_id" : ObjectId("5e3999fb9e4f06af55199805"), "Names" : [ "Chris", "David", "Bob" ] } { "_id" : ObjectId("5e399a0d9e4f06af55199806"), "Names" : [ "Chris", "Mike" ] } { ...
Read MoreQuery MongoDB subdocument to print on one line?
To display subdocuments in one line, use $unwind along with aggregate(). Let us create a collection with documents −> db.demo183.insertOne( ... { ... "_id": "110", ... "DueDate": ISODate("2020-02-04T01:10:42.000Z"), ... "ProductDetails": [ ... { ... "ProductName": "Product-1", ... "isAvailable": true ... }, ... { ... "ProductName": "Product-2", ... "isAvailable": false ... } ... ] ... } ...); { "acknowledged" : true, "insertedId" : "110" }Display all documents from a collection with the ...
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