To add a new field, use the $addFields in MongoDB. Let us create a collection with documents −> db.demo719.insertOne( ...    { ...       "Number":"7374644", ...       "details" : { ...          "otherDetails" : [ ...             { ...                "ProductId" :"102", ...                "ProductPrice" : NumberInt(500) ...             }, ...             { ...                "ProductId" :"103", ...     ... Read More

The task is to convert the distance from kilometers to meters and centimeters in PL/SQL.PL/SQL is the extension of SQL which combines the Data manipulation of SQL with the working of procedural language.According to the problem we should have distance in kilometers whose value we have to convert in meters and centimeters.As per the conversion rule −1km = 1000 meters1km = 100000 centimetersAccording to this conversion rule we want the distance to be converted by a logic in PL/SQL.ExampleInput: kilometer = 10 Output: meter = 10000    Centimeter = 1000000 Input: kilometer = 9 Output: meter = 9000    Centimeter ... Read More

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