For this, use aggregate() in MongoDB. Let us first create a collection with documents −> db.demo126.insertOne( ...    { ...       "StudentDetails" : { ...          "Number" : 1, ...          "OtherDetails" : [ ...          { ...   ... Read More

To remove a specific element, use $pull. Let us create a collection with documents −> db.demo125.insertOne({"ListOfNames":["John", "Chris", "Bob", "David", "Carol"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f304068e7f832db1a7f55") }Display all documents from a collection with the help of find() method −> db.demo125.find().pretty();This will produce the following output −{   ... Read More

For this, use find() along with update(). Let us create a collection with documents −> db.demo124.insertOne( ...    { ...       "Name" : "John", ...       "Id" : 101, ...       "ProjectDetails" : [{ ...          "ProjectName1" : "Online Book", ... ... Read More

Let us create a collection with documents −> db.demo123.insertOne({"ListOfSubject":['MySQL', 'MongoDB', 'Java']}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f24ac140daf4c2a3544b8") } > db.demo123.insertOne({"ListOfSubject":['Python', 'MongoDB', 'C']}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f24cd140daf4c2a3544b9") } > db.demo123.insertOne({"ListOfSubject":['MySQL', 'MongoDB', 'C++']}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f24ce140daf4c2a3544ba") }Display all ... Read More

To get distinct levels of array field, use $addToSet in MongoDB. Let us create a collection with documents −> db.demo122.insertOne({"ListOfValues":[100, 10]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f20f1140daf4c2a3544b6") } > db.demo122.insertOne({"ListOfValues":[240, 10]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f20f7140daf4c2a3544b7") }Display all documents from a collection with ... Read More

Let us first create a collection with documents −> db.demo121.insertOne( ...    { ...       "Id" : 101, ...       "Details" : [ ...          { ...             "SubjectId" : "1", ...             ... Read More

For this, use aggregate() in MongoDB. Let us create a collection with documents −> db.demo120.insertOne( ...    { ...       'Name': 'Chris', ...       'Subjects': [ 'MySQL', 'MongoDB', 'Java', 'Python' ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2f11aed8f64a552dae6365") } ... Read More

To prevent duplicates of multiple fields, use ensureIndex() and set unique:true. Let us create a collection with documents −> db.demo272.ensureIndex({"FirstName":1, "Subject":1}, {unique:true}); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 } > db.demo272.insertOne({"FirstName":"Chris", "Subject":"MySQL"}); {    "acknowledged" : true,    "insertedId" ... Read More

Set a custom variable and use update() along with $inc to increment. Let us create a collection with documents −> db.demo271.insertOne({"Marks":56}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4821211627c0c63e7dbabc") } > db.demo271.insertOne({"Marks":78}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4821241627c0c63e7dbabd") } > db.demo271.insertOne({"Marks":72}); {    "acknowledged" : true, ... Read More

Let us first create a collection with documents −> db.demo270.insertOne({"ClientName":"Chirs", "Age":34}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e481e371627c0c63e7dbab8") } > db.demo270.insertOne({"ClientName":"David", "Age":31}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e481e3d1627c0c63e7dbab9") } > db.demo270.insertOne({"ClientName":"Bob", "Age":31}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e481e431627c0c63e7dbaba") } > db.demo270.insertOne({"ClientName":"Carol", "Age":36}); ... Read More