To get the first and last document in MongoDB, use aggregate() along with $first and $last respectively. Let us create a collection with documents −> db.demo73.insertOne({"Name":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29c41b71bf0181ecc4226c") } . > db.demo73.insertOne({"Name":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29c41e71bf0181ecc4226d") } > db.demo73.insertOne({"Name":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29c42271bf0181ecc4226e") }Display all documents from a collection with the help of find() method −> db.demo73.find();This will produce the following output −{ "_id" : ObjectId("5e29c41b71bf0181ecc4226c"), "Name" : "Chris" } { "_id" : ObjectId("5e29c41e71bf0181ecc4226d"), "Name" : "Bob" } { "_id" : ObjectId("5e29c42271bf0181ecc4226e"), "Name" ... Read More

For this, use $let along with $expr. Here, $let is used to define temporary variable. The $expr is used for aggregation expressions. Let us create a collection with documents −> db.demo72.insertOne( ... { ...    StudentDetails:[ ...       { ...          Name: "Chris", ...          Age: 21 ...       }, ...       { ...          Name: "David", ...          Age: 23 ...       }, ...       { ...          Name: "Bob", ...       ... Read More

To calculate sum of string in MongoDB, use aggregate(). Let us create a collection with documents −> db.demo71.insertOne({"Price":"20"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29af210912fae76b13d76e") } > db.demo71.insertOne({"Price":"50"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29af240912fae76b13d76f") } > db.demo71.insertOne({"Price":"20"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29af270912fae76b13d770") } > db.demo71.insertOne({"Price":"10"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e29af2d0912fae76b13d771") }Display all documents from a collection with the help of find() method −> db.demo71.find();This will produce the following output −{ "_id" : ObjectId("5e29af210912fae76b13d76e"), "Price" : "20" } { "_id" : ObjectId("5e29af240912fae76b13d76f"), "Price" : "50" } { "_id" ... Read More

Concatenate deep sub-lists using aggregate() along with $unwind. Let us create a collection with documents −> db.demo70.insertOne( ...    { ... ...       "first" : [ ...          { ...             "details" : { ...                "second" : [ ...                   { ...                      "StudentDetails" : { ...                      "Score" : 10 ...           ... Read More

For this, use $where and compare with ==. Let us create a collection with documents −> db.demo69.insertOne( ... { ...    "_id" : ObjectId("507c7f79bcf86cd7994f6c0e"), ... "Details" : { ... ...    "id" : ObjectId("507c7f79bcf86cd7994f6c0e") ...    } ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("507c7f79bcf86cd7994f6c0e") } > db.demo69.insertOne( ... { ...    "_id" : ObjectId("507c7f79bcf86cd7994f6c0f"),    "Details" : { ...    "id" :ObjectId("507c7f79bcf86cd7994f6c0a") ...    } ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("507c7f79bcf86cd7994f6c0f") }Display all documents from a collection with the help of find() method −> db.demo69.find();This will produce ... Read More

To sort, use $match along with aggregate. Let us create a collection with documents −> db.demo67.insertOne({"StudentAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e289edf602d9a2ff1828ed8") } > db.demo67.insertOne({"StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e289ee1602d9a2ff1828ed9") } > db.demo67.insertOne({"StudentAge":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e289ee3602d9a2ff1828eda") }Display all documents from a collection with the help of find() method −> db.demo67.find();This will produce the following output −{ "_id" : ObjectId("5e289edf602d9a2ff1828ed8"), "StudentAge" : 23 } { "_id" : ObjectId("5e289ee1602d9a2ff1828ed9"), "StudentAge" : 21 } { "_id" : ObjectId("5e289ee3602d9a2ff1828eda"), "StudentAge" : 24 }Following is the query to sort with aggregate in ... Read More

To get index of an array element, use $indexOfArray. Let us create a collection with documents −> db.demo65.insertOne({"ListOfValues":[10, 20, 30]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28990ecfb11e5c34d89938") } > db.demo65.insertOne({"ListOfValues":[50, 60, 70, 100]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28991ecfb11e5c34d89939") } > db.demo65.insertOne({"ListOfValues":[30, 40, 89, 91, 98]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28992bcfb11e5c34d8993a") }Display all documents from a collection with the help of find() method −> db.demo65.find();This will produce the following output −{ "_id" : ObjectId("5e28990ecfb11e5c34d89938"), "ListOfValues" : [ 10, 20, 30 ] } { "_id" : ObjectId("5e28991ecfb11e5c34d89939"), "ListOfValues" : [ 50, 60, ... Read More

To calculate average of a particular field, use aggregate() along with $avg. Let us create a collection with documents −> db.demo214.insertOne({"Marks":56, "Name":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e319403d395bdc2134705") } > db.demo214.insertOne({"Marks":86, "Name":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e319c03d395bdc2134706") } > db.demo214.insertOne({"Marks":78, "Name":"Carol"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e31a403d395bdc2134707") }Display all documents from a collection with the help of find() method −> db.demo214.find();This will produce the following output −{ "_id" : ObjectId("5e3e319403d395bdc2134705"), "Marks" : 56, "Name" : "David" } { "_id" : ObjectId("5e3e319c03d395bdc2134706"), "Marks" : 86, "Name" : "Bob" } { "_id" ... Read More

To merge, use aggregate() along with $PUSH. Let us create a collection with documents −> db.demo64.insertOne({"Subjects":["MySQL", "MongoDB", "Java"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28762bcfb11e5c34d89936") } > db.demo64.insertOne({"Subjects":["Oracle", "Spring", "Python"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28763fcfb11e5c34d89937") }Display all documents from a collection with the help of find() method −> db.demo64.find();This will produce the following output −{ "_id" : ObjectId("5e28762bcfb11e5c34d89936"), "Subjects" : [ "MySQL", "MongoDB", "Java" ] } { "_id" : ObjectId("5e28763fcfb11e5c34d89937"), "Subjects" : [ "Oracle", "Spring", "Python" ] }Following is the query to merge array of document in MongoDB −> db.demo64.aggregate([ ... { "$group": { ... Read More

You need to use $group to group documents with specified _id expression. Let us first create a collection with documents −> db.aggreagateDemo.insertOne({"Product_Id":1, "ProductPrice":50}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3c025ddae1f53b621d9") } > db.aggreagateDemo.insertOne({"Product_Id":2, "ProductPrice":100}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3c625ddae1f53b621da") } > db.aggreagateDemo.insertOne({"Product_Id":2, "ProductPrice":500}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3cb25ddae1f53b621db") } > db.aggreagateDemo.insertOne({"Product_Id":1, "ProductPrice":150}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3d125ddae1f53b621dc") }Following is the query to display all documents from a collection with the help of find() method −> db.aggreagateDemo.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e06d3c025ddae1f53b621d9"), ... Read More