Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
To display only unique records, use distinct() in MongoDB. Let us create a collection with documents −> db.demo613.insertOne({"Name":"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988bd4f6b89257f5584d88") } > db.demo613.insertOne({"Name":"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988bdbf6b89257f5584d89") } > db.demo613.insertOne({"Name":"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988bddf6b89257f5584d8a") } > db.demo613.insertOne({"Name":"David"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988be0f6b89257f5584d8b") } > db.demo613.insertOne({"Name":"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988be2f6b89257f5584d8c") } > db.demo613.insertOne({"Name":"Sam"});{ "acknowledged" : true, "insertedId" : ObjectId("5e988be8f6b89257f5584d8d") }Display all documents from a collection with the help of find() method −> db.demo613.find();This will produce the following output −{ "_id" : ObjectId("5e988bd4f6b89257f5584d88"), "Name" : ... Read More
Check for a specific field using MongoDB $exists. If that field does not exist in a document, then you need to display the same document with find().Let us create a collection with documents −> db.demo612.insertOne({id:1, "Info":[{Name:"Chris", Age:21}, {Name:"David"}]});{ "acknowledged" : true, "insertedId" : ObjectId("5e987372f6b89257f5584d87") }Display all documents from a collection with the help of find() method −> db.demo612.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e987372f6b89257f5584d87"), "id" : 1, "Info" : [ { "Name" : "Chris", "Age" : 21 }, ... Read More
To sort documents in MongoDB 4, use sort(). To show only a single field, which is sorted, set it to 1.Let us create a collection with documents −> db.demo611.insertOne({"Name":"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e987110f6b89257f5584d83") } > db.demo611.insertOne({"Name":"Adam"});{ "acknowledged" : true, "insertedId" : ObjectId("5e987115f6b89257f5584d84") } > db.demo611.insertOne({"Name":"John"});{ "acknowledged" : true, "insertedId" : ObjectId("5e987118f6b89257f5584d85") } > db.demo611.insertOne({"Name":"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e98711bf6b89257f5584d86") }Display all documents from a collection with the help of find() method −> db.demo611.find(); This will produce the following output: { "_id" : ObjectId("5e987110f6b89257f5584d83"), "Name" : "Chris" } { "_id" : ObjectId("5e987115f6b89257f5584d84"), "Name" : ... Read More
To add together a subset of elements of an array, use $first along with $sum. Let us create a collection with documents −> db.demo610.insertOne({Values:[10, 20, 30, 40, 50]});{ "acknowledged" : true, "insertedId" : ObjectId("5e9747b8f57d0dc0b182d62e") }Display all documents from a collection with the help of find() method −> db.demo610.find().pretty()This will produce the following output −{ "_id" : ObjectId("5e9747b8f57d0dc0b182d62e"), "Values" : [ 10, 20, 30, 40, 50 ] }Here is the query to add together a subset of elements of an array in ... Read More
To remove the entire array from the collection, use $unset in MongoDB. Let us create a collection with documents −> db.demo609.insertOne({"ListOfSubject":["MySQL", "MongoDB"]});{ "acknowledged" : true, "insertedId" : ObjectId("5e974695f57d0dc0b182d62c") } > db.demo609.insertOne({"ListOfSubject":["Java"]});{ "acknowledged" : true, "insertedId" : ObjectId("5e97469af57d0dc0b182d62d") }Display all documents from a collection with the help of find() method −> db.demo609.find();This will produce the following output −{ "_id" : ObjectId("5e974695f57d0dc0b182d62c"), "ListOfSubject" : [ "MySQL", "MongoDB" ] } { "_id" : ObjectId("5e97469af57d0dc0b182d62d"), "ListOfSubject" : [ "Java" ] }Here is the query to remove the entire array from collection −> db.demo609.update({}, {$unset:{"ListOfSubject":""}}, {multi:true}); WriteResult({ "nMatched" : 2, "nUpserted" : 0, ... Read More
To get unique values within two arrays in a document, use a $setUnion in aggregate(). The $setUnion takes two or more arrays and returns an array containing the elements that appear in any input array.Let us create a collection with documents −>db.demo608.insertOne({"ListOfName1":["John", "Chris", "Bob", "David"], "ListOfName2":["Bob", "Sam", "John", "Robert", "Chris"]} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e974542f57d0dc0b182d62b") }Display all documents from a collection with the help of find() method −> db.demo608.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e974542f57d0dc0b182d62b"), "ListOfName1" : [ "John", "Chris", ... Read More
To update the nested document, use update() and within that, use dot notation. Let us create a collection with documents −> db.demo607.insertOne( ... { ... id:1, ... "Info1" : { ... "Name" : "Chris", ... "Age" : 21, ... ... "Info2" : { ... "SubjectName" : "MongoDB", ... "Marks" : 89 ... } ... } ... } ... ); { ... Read More
For average in MongoDB, use the $avg. Let us create a collection with documents. Here, we have duplicate ids with rating for each −> db.demo606.insertOne({id:1, rating:5});{ "acknowledged" : true, "insertedId" : ObjectId("5e972dfbf57d0dc0b182d623") } > db.demo606.insertOne({id:1, rating:4});{ "acknowledged" : true, "insertedId" : ObjectId("5e972dfef57d0dc0b182d624") } > db.demo606.insertOne({id:2, rating:3});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e09f57d0dc0b182d625") } > db.demo606.insertOne({id:1, rating:null});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e0ef57d0dc0b182d626") } > db.demo606.insertOne({id:2, rating:null});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e15f57d0dc0b182d627") } > db.demo606.insertOne({id:2, rating:3});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e1bf57d0dc0b182d628") }Display all documents from a collection with the help of find() method ... Read More
For this, use UPDATE() method and within that set the two conditions. Let us create a collection with documents −> db.demo605.insertOne( ... { ... _id:1, ... "Information" : [ ... { ... "id" : "Product-1", ... "Quantity" : 50, ... }, ... { ... "id" : "Product-2", ... "Quantity" : 100, ... }, ... Read More
For this, set “unique:true” i.e. the unique constraint and avoid inserting duplicates as in the below syntax −db.yourCollectionName.ensureIndex({yourFieldName: 1}, {unique: true, dropDups: true})To understand the above syntax, let us create a collection with documents. Here, duplicate insertion won’t be allowed −> db.demo604.ensureIndex({FirstName: 1}, {unique: true, dropDups: true});{ "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo604.insertOne({FirstName:"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960887ed011c280a0905d8") } > db.demo604.insertOne({FirstName:"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088aed011c280a0905d9") } > db.demo604.insertOne({FirstName:"David"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088ded011c280a0905da") } > db.demo604.insertOne({FirstName:"Chris"}); 2020-04-15T00:31:35.978+0530 ... Read More