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Database Articles
Page 231 of 546
MongoDB $elemMatch to match document
Let us create a collection with documents −> db.demo313.insertOne({"_id":100, "details":[{"Name":"Chris", "Age":24}]}); { "acknowledged" : true, "insertedId" : 100 } > db.demo313.insertOne({"_id":101, "details":[{"Name":"David", "Age":22}]}); { "acknowledged" : true, "insertedId" : 101 } > db.demo313.insertOne({"_id":102, "details":[{"Name":"Mike", "Age":25}]}); { "acknowledged" : true, "insertedId" : 102 }Display all documents from a collection with the help of find() method −> db.demo313.find();This will produce the following output −{ "_id" : 100, "details" : [ { "Name" : "Chris", "Age" : 24 } ] } { "_id" : 101, "details" : [ { "Name" : "David", "Age" : 22 } ] } { "_id" : 102, "details" ...
Read MoreMongoDB - update partial number of documents?
To update partial number of documents, set multi to true. Let us create a collection with documents −> db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce16f8647eb59e56204a") } > db.demo312.insertOne({"FirstName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce19f8647eb59e56204b") } > db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce1cf8647eb59e56204c") } > db.demo312.insertOne({"FirstName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce20f8647eb59e56204d") } > db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce22f8647eb59e56204e") }Display all documents from a collection with the help of find() method −> db.demo312.find();This will produce the following output −{ "_id" : ObjectId("5e50ce16f8647eb59e56204a"), "FirstName" ...
Read MoreGet the count of a specific value in MongoDB quickly
For faster queries, create an index. To get the count, use count(). Let us create a collection with documents −> db.demo311.ensureIndex({"Name":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo311.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd01f8647eb59e562044") } > db.demo311.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd05f8647eb59e562045") } > db.demo311.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd06f8647eb59e562046") } > db.demo311.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd0af8647eb59e562047") } > db.demo311.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd0df8647eb59e562048") } > db.demo311.insertOne({"Name":"Chris"}); { ...
Read MoreRetrieving a Subset of Fields from MongoDB
To retried a subset of fields, use dot notation in find(). Let us create a collection with documents −> db.demo307.insertOne({ ... "CleintId":101, ... "ClientDetails":{"ClientFirstName":"Chris", "Age":34}, ... "ClientCountryName":"US" ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e4eab88f8647eb59e56203c") } > db.demo307.insertOne({ ... "CleintId":102, ... "ClientDetails":{"ClientFirstName":"David", "Age":31}, ... "ClientCountryName":"UK" ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e4eab97f8647eb59e56203d") }Display all documents from a collection with the help of find() method −> db.demo307.find();This will produce the following output −{ "_id" : ObjectId("5e4eab88f8647eb59e56203c"), "CleintId" : 101, "ClientDetails" : { "ClientFirstName" : "Chris", "Age" : 34 ...
Read MoreFetching all documents from MongoDB Collection in a beautified form
To fetch documents, use find() in MongoDB. With that, to format the resultant documents, use pretty().Let us create a collection with documents −> db.demo306.insertOne({"Name":"Robert", "Age":21}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7c6f8647eb59e562038") } > db.demo306.insertOne({"Name":"David", "Age":23}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7cdf8647eb59e562039") } > db.demo306.insertOne({"Name":"Mike", "Age":25}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7d4f8647eb59e56203a") } > db.demo306.insertOne({"Name":"Carol", "Age":26}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7dcf8647eb59e56203b") }Display all documents from a collection with the help of find() method −> db.demo306.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e4ea7c6f8647eb59e562038"), "Name" : ...
Read MoreHow to get the child of a MongoDB collection by the key?
To get the child of a collection in MongoDB, use find(). Let us create a collection with documents −> db.demo305.insertOne( ... { ... _id: 101, ... FirstName : 'Chris', ... details : { ... "0":"102", ... "1":"10001" ... } ... } ...); { "acknowledged" : true, "insertedId" : 101 } > db.demo305.insertOne( ... { ... _id: 102, ... FirstName : 'David', ... details : { ... "0":"103", ... "1":"10002" ... } ... } ...); { "acknowledged" : true, "insertedId" : 102 }Display all documents from a collection with the help of find() method −> db.demo305.find();This will produce the following output −{ "_id" : 101, "FirstName" : "Chris", "details" : { "0" : "102", "1" : "10001" } } { "_id" : 102, "FirstName" : "David", "details" : { "0" : "103", "1" : "10002" } }Following is the query to get the child of a MongoDB collection by the key −> db.demo305.find({_id:102},{'details.0':1});This will produce the following output −{ "_id" : 102, "details" : { "0" : "103" } }
Read MoreFind values with OR operator in MongoDB and format the result.?
Use $or operator to fetch values and to format the result, use “pretty()”. Let us create a collection with documents −> db.demo304.insertOne({"StudentName":"Chris", "StudentAge":23}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea3ccf8647eb59e562034") } > db.demo304.insertOne({"StudentName":"David", "StudentAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea3d7f8647eb59e562035") } > db.demo304.insertOne({"StudentName":"Mike", "StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea3e2f8647eb59e562036") } > db.demo304.insertOne({"StudentName":"Carol", "StudentAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea3eef8647eb59e562037") }Display all documents from a collection with the help of find() method −> db.demo304.find();This will produce the following output −{ "_id" : ObjectId("5e4ea3ccf8647eb59e562034"), "StudentName" : "Chris", "StudentAge" : 23 ...
Read MoreMongoDB query to get distinct FirstName values from documents
For distinct values, use distinct(). Let us create a collection with documents −> db.demo303.insertOne({FirstName:"Chris", LastName:"Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea0f6f8647eb59e56202f") } > db.demo303.insertOne({FirstName:"John", LastName:"Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea104f8647eb59e562030") } > db.demo303.insertOne({FirstName:"Chris", LastName:"Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea10df8647eb59e562031") } > db.demo303.insertOne({FirstName:"John", LastName:"Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea121f8647eb59e562032") } > db.demo303.insertOne({FirstName:"David", LastName:"Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea136f8647eb59e562033") }Display all documents from a collection with the help of find() method −> db.demo303.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e4ea0f6f8647eb59e56202f"), ...
Read MoreField selection within MongoDB query using dot notation?
For this, use dot notation for field selection in MongoDB find(). Let us create a collection with documents −> db.demo302.insertOne({"Id":101, "details":[{"Name":"Chris", Age:21, "Subject":"MySQL"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e4d746f5d93261e4bc9ea52") } > db.demo302.insertOne({"Id":102, "details":[{"Name":"Bob", Age:23, "Subject":"MongoDB"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e4d74815d93261e4bc9ea53") } > db.demo302.insertOne({"Id":103, "details":[{"Name":"David", Age:20, "Subject":"Java"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e4d74955d93261e4bc9ea54") }Display all documents from a collection with the help of find() method −> db.demo302.find();This will produce the following output −{ "_id" : ObjectId("5e4d746f5d93261e4bc9ea52"), "Id" : 101, "details" : [ { "Name" : "Chris", "Age" : 21, "Subject" : ...
Read MoreMongoDB query to change order of array elements?
Use swap concept to change the order of array elements. Let us create a collection with documents −> db.demo301.insertOne({"Name":["Chris", "David", "Bob"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e4d6ff55d93261e4bc9ea51") }Display all documents from a collection with the help of find() method −> db.demo301.find();This will produce the following output −{ "_id" : ObjectId("5e4d6ff55d93261e4bc9ea51"), "Name" : [ "Chris", "David", "Bob" ] }Following is the query to change the order of array elements −> db.demo301.find({}, { Name : 1 }).forEach(function(n) { ... var t = n.Name[0]; ... n.Name[0] = n.Name[1]; ... n.Name[1] = t; ... db.demo301.update({ _id: n._id ...
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