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Database Articles
Page 204 of 546
Get specific elements from embedded array in MongoDB?
To get specific elements, use $match with dot notation. Let us create a collection with documents −> db.demo641.insert( ... { ... ProductId:101, ... "ProductInformation": ... ( [ ... { ... ProductName:"Product-1", ... "ProductPrice":1000 ... }, ... { ... ProductName:"Product-2", ... "ProductPrice":500 ... ...
Read MoreFiltering MongoDB items by fields and subfields?
To filter items by fields and subfields, use dot notation. Let us create a collection with documents −> db.demo638.insert({Name:"Chris"}); WriteResult({ "nInserted" : 1 }) > db.demo638.insert({Name:"David", details:{Subject:"MongoDB"}}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo638.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e9c28666c954c74be91e6de"), "Name" : "Chris" } { "_id" : ObjectId("5e9c28866c954c74be91e6df"), "Name" : "David", "details" : { "Subject" : "MongoDB" } }Following is the query to filter items by multiple fields and subfields −> ...
Read MoreMongoDB - interpret information on the query plan for the db.collection.find() method
For information on the query plan, use explain() in MongoDB. Let us create a collection with documents −> db.demo637.ensureIndex({ClientName:1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo637.insert({ClientName:"John"}); WriteResult({ "nInserted" : 1 }) > db.demo637.insert({ClientName:"Bob"}); WriteResult({ "nInserted" : 1 }) > db.demo637.insert({ClientName:"Johnson"}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo637.find();This will produce the following output −{ "_id" : ObjectId("5e9c26916c954c74be91e6db"), "ClientName" : "John" } { "_id" : ObjectId("5e9c26936c954c74be91e6dc"), "ClientName" : "Bob" } { "_id" : ObjectId("5e9c269d6c954c74be91e6dd"), "ClientName" : "Johnson" }Case ...
Read MoreMongoDB query to display alternative documents with mapReduce() function and emit even field values
Let us create a collection with documents −> db.demo636.insert({id:1}); WriteResult({ "nInserted" : 1 }) > db.demo636.insert({id:2}); WriteResult({ "nInserted" : 1 }) > db.demo636.insert({id:3}); WriteResult({ "nInserted" : 1 }) > db.demo636.insert({id:4}); WriteResult({ "nInserted" : 1 }) > db.demo636.insert({id:5}); WriteResult({ "nInserted" : 1 }) > db.demo636.insert({id:6}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo636.find();This will produce the following output −{ "_id" : ObjectId("5e9c127b6c954c74be91e6d2"), "id" : 1 } { "_id" : ObjectId("5e9c127e6c954c74be91e6d3"), "id" : 2 } { "_id" : ObjectId("5e9c127f6c954c74be91e6d4"), "id" : 3 } { "_id" : ObjectId("5e9c12816c954c74be91e6d5"), "id" : 4 } { ...
Read MoreCalculate frequency of duplicate names from NAME field using MongoDB aggregate?
To calculate frequency, group with $group in aggregate(). Let us create a collection with documents −> db.demo635.insertOne({Name:"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10f06c954c74be91e6cc") } > db.demo635.insertOne({Name:"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10f46c954c74be91e6cd") } > db.demo635.insertOne({Name:"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10f66c954c74be91e6ce") } > db.demo635.insertOne({Name:"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10f86c954c74be91e6cf") } > db.demo635.insertOne({Name:"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10fb6c954c74be91e6d0") } > db.demo635.insertOne({Name:"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c10fc6c954c74be91e6d1") }Display all documents from a collection with the help of find() method −> db.demo635.find();This ...
Read MoreHow to update document with marks value in MongoDB for student David
Use forEach() and traverse to find student name David update new marks for the same student. Let us create a collection with documents −> db.demo634.insertOne({Name:"Chris", "Marks":76}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0ea66c954c74be91e6c9") } > db.demo634.insertOne({Name:"Bob", "Marks":67}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0ead6c954c74be91e6ca") } > db.demo634.insertOne({Name:"David", "Marks":37}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0eb76c954c74be91e6cb") }Display all documents from a collection with the help of find() method −> db.demo634.find();This will produce the following output −{ "_id" : ObjectId("5e9c0ea66c954c74be91e6c9"), "Name" : "Chris", "Marks" : 76 } { "_id" : ObjectId("5e9c0ead6c954c74be91e6ca"), "Name" : "Bob", "Marks" : ...
Read MoreRemove values from a matrix like document in MongoDB
To remove values from a matrix, use $pull in MongoDB. Let us create a collection with documents −> db.demo632.insertOne( ... { ... "arrayMatrix": [ ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20] ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e9b27b46c954c74be91e6c0") }Display all documents from a collection with the help of find() ...
Read MoreReturn specific MongoDB embedded document
Use $unwind twice for specific embedded document in MongoDB. Let us create a collection with documents −> db.demo631.insert( ... { ... id: "101", ... Info1: [ ... { ... CountryName : "US", ... Info2 : [ ... { ... Name:"Chris", ... Age:24 ... }, { ...
Read MoreQuery for values (not objects) in list with MongoDB
To query for values in list, use positional operator($) in MongoDB. Let us create a collection with documents −> db.demo628.insertOne({id:1, Name:["Chris", "David", "John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae7ea6c954c74be91e6b6") } > db.demo628.insertOne({id:1, Name:["Carol", "Sam"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae7f26c954c74be91e6b7") } > db.demo628.insertOne({id:2, Name:["Mike", "Sam", "John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae8056c954c74be91e6b8") }Display all documents from a collection with the help of find() method −> db.demo628.find();This will produce the following output −{ "_id" : ObjectId("5e9ae7ea6c954c74be91e6b6"), "id" : 1, "Name" : [ "Chris", "David", "John" ] } { "_id" : ObjectId("5e9ae7f26c954c74be91e6b7"), "id" ...
Read MoreSum with MongoDB group by multiple columns to calculate total marks with duplicate ids
For this, use aggregate() along with $group. Let us create a collection with documents −> db.demo627.insertOne({id:101, "Name":"Chris", "Marks":54}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb306c954c74be91e6b2") } > db.demo627.insertOne({id:102, "Name":"Bob", "Marks":74}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb3c6c954c74be91e6b3") } > db.demo627.insertOne({id:101, "Name":"Chris", "Marks":87}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb426c954c74be91e6b4") } > db.demo627.insertOne({id:102, "Name":"Mike", "Marks":70}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb4b6c954c74be91e6b5") }Display all documents from a collection with the help of find() method −> db.demo627.find();This will produce the following output −{ "_id" : ObjectId("5e9acb306c954c74be91e6b2"), "id" : 101, "Name" : "Chris", "Marks" : ...
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