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Big Data Analytics Articles
Page 6 of 135
MongoDB query to update nested document
To update a nested document in MongoDB, use the $ positional operator with the $set operator. The $ operator identifies the array element that matches the query condition and allows you to update specific fields within that element. Syntax db.collection.update( {"arrayName.field": "matchValue"}, { $set: { "arrayName.$.field": "newValue" } } ); Create Sample Data Let us create a collection with documents − db.demo595.insertOne({ "Information": [ { "_id": new ObjectId(), "Name": "Chris" }, ...
Read MoreMongoDB query to limit the returning values of a field?
To limit the returning values of a field in MongoDB, use the $slice operator in the projection parameter of the find() method. This is particularly useful for limiting array elements returned in query results. Syntax db.collection.find( {}, { "arrayField": { "$slice": numberOfElements } } ); Sample Data db.demo594.insertOne({ id: 1, details: [ { Name: "Chris", Age: 21 }, { Name: "Bob", ...
Read MoreFetch specific multiple documents in MongoDB
To fetch specific multiple documents in MongoDB, use the $in operator to match documents where a field value equals any value in a specified array. Syntax db.collection.find({ "field": { $in: [value1, value2, value3, ...] } }); Sample Data Let us create a collection with documents − db.demo593.insertMany([ { id: 1, "Name": "Chris" }, { id: 2, "Name": "John" }, { id: 3, "Name": "Bob" }, { id: 4, "Name": "Sam" } ]); ...
Read MoreMongoDB query to match documents that contain an array field
To match documents that contain an array field, use the $elemMatch operator. This operator matches documents where at least one array element meets all specified criteria within a single element. Syntax db.collection.find({ "arrayField": { "$elemMatch": { "field1": "value1", "field2": "value2" } } }); Sample Data Let ...
Read MoreMongoDB query to find "where" Billing Address is Equal to Delivery Address from documents?
To find documents where billing address equals delivery address in MongoDB, use the $where operator with JavaScript expressions to compare field values within the same document. Syntax db.collection.find({ $where: "this.field1 == this.field2" }); Sample Data db.demo589.insertMany([ {deliveryAddress: "US", billingAddress: "UK"}, {deliveryAddress: "US", billingAddress: "US"}, {deliveryAddress: "US", billingAddress: "AUS"}, {deliveryAddress: "UK", billingAddress: "US"} ]); { "acknowledged" : true, "insertedIds" : [ ...
Read MoreMongoDB query to gather unique array item?
To gather unique array items from a MongoDB collection, use the distinct() method. This method returns an array of unique values for a specified field, automatically removing duplicates. Syntax db.collection.distinct("fieldName") Sample Data Let us create a collection with documents ? db.demo588.insertOne({ "CountryName": ["US", "AUS", "UK", "US", "UK", "AUS"] }); { "acknowledged": true, "insertedId": ObjectId("5e92bbd2fd2d90c177b5bccb") } Display all documents from the collection ? db.demo588.find().pretty(); { "_id": ObjectId("5e92bbd2fd2d90c177b5bccb"), ...
Read MoreHow to keep appending subdocuments in MongoDB?
To append subdocuments in MongoDB, use the $push operator with the update() method. This operator adds new subdocuments to an existing array field without removing existing elements. Syntax db.collection.update( { "field": "matchValue" }, { "$push": { "arrayField": { subdocumentData } } } ); Sample Data Let us create a collection with documents − db.demo587.insertMany([ { "id": 101, "details": [{ Name: "Chris", Age: 21, Marks: 57 }] }, { "id": 102, "details": [{ Name: "Bob", Age: 22, ...
Read MoreMongoDB: Using reference as key and manually adding a value?
To manually add a value to an array in MongoDB using a reference as a key, use the $push operator. This allows you to add new elements to existing arrays, including complex objects with multiple fields. Syntax db.collection.update( { "field": "matchValue" }, { "$push": { "arrayField": newValue } } ); Sample Data db.demo585.insertMany([ { firstName: "John", lastName: "Doe", ...
Read MoreHow to project grouping into object in MongoDB and display only the marks field?
To project grouping into an object in MongoDB and display only the marks field, you can use JavaScript methods to transform array data into key-value objects. This approach converts subject-marks pairs into a single object where subject names become keys and marks become values. Syntax var resultObject = {}; arrayData.forEach(function(item) { resultObject[item.keyField] = item.valueField; }); Sample Data var document = [ { "SubjectName": "MySQL", "Marks": 78 }, { "SubjectName": "MongoDB", "Marks": 89 }, { "SubjectName": "Java", "Marks": ...
Read MoreMongoDB query to get average in aggregation of array element?
To calculate the average of array elements in MongoDB, use the $avg operator in an aggregation pipeline. This operator computes the arithmetic mean of all numeric values in an array field. Syntax db.collection.aggregate([ { $project: { fieldName: { $avg: "$arrayField" } } } ]) Sample Data Let us create a collection with documents containing an array of marks ? db.demo584.insertOne({ "Marks": [75, 50, 85, 60, 80] }); { "acknowledged": true, "insertedId": ObjectId("5e91d827fd2d90c177b5bcc2") } ...
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