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Big Data Analytics Articles
Page 59 of 135
Insert in MongoDB without duplicates
To insert records in MongoDB and avoid duplicates, create a unique index on the field that should not contain duplicate values. When you attempt to insert a document with a duplicate value, MongoDB will reject the operation with an error. Syntax db.collection.createIndex({"fieldName": 1}, { unique: true }); db.collection.insert({"fieldName": "value"}); Example Let's create a unique index on the StudentFirstName field and attempt to insert duplicate records ? Step 1: Create Unique Index db.insertWithoutDuplicateDemo.createIndex({"StudentFirstName":1}, { unique: true }); { "createdCollectionAutomatically" : true, "numIndexesBefore" : ...
Read MoreApply a condition inside subset in MongoDB Aggregation?
To apply a condition inside subset in MongoDB aggregation, use $setIsSubset. This operator checks whether a specified set is a subset of another set, returning true if all elements exist in the target array. Syntax { $setIsSubset: [, ] } Sample Data db.subsetDemo.insertMany([ { "StudentName": "Chris", "StudentFavouriteSubject": ["Java", "Python"] }, { "StudentName": "Chris", ...
Read MoreGetting MongoDB results from the previous month
To get MongoDB results from the previous month, first get the current date and subtract one month from it. This creates a date boundary to filter records that fall within the previous month period. Syntax var previousMonth = new Date(); previousMonth.setMonth(previousMonth.getMonth() - 1); db.collection.find({dateField: {$gte: previousMonth}}); Sample Data db.findOneMonthAgoData.insertMany([ {"CustomerName": "Chris", "PurchaseDate": new ISODate("2019-12-26")}, {"CustomerName": "David", "PurchaseDate": new ISODate("2019-11-26")}, {"CustomerName": "Bob", "PurchaseDate": new ISODate("2020-11-26")} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreHow can I aggregate nested documents in MongoDB?
To aggregate nested documents in MongoDB, you can use the aggregation pipeline with operators like $unwind and $group. The $unwind operator flattens array fields, allowing you to process individual elements within nested structures. Syntax db.collection.aggregate([ { $unwind: "$arrayField" }, { $unwind: "$arrayField.nestedArray" }, { $group: { _id: null, result: { $operation: "$arrayField.nestedArray.field" } } } ]); Sample Data db.aggregateDemo.insertMany([ { "ProductInformation": [ ...
Read MoreHow to add a column in MongoDB collection?
To add a column (field) in MongoDB, you need to update the collection using the $set operator. Since MongoDB is schema-less, adding a new field means updating existing documents to include the new field. Syntax db.collection.updateMany({}, {$set: {"newColumnName": "value"}}); Sample Data Let us create a collection with some sample documents ? db.addColumnDemo.insertMany([ {"StudentId": 101, "StudentName": "Chris"}, {"StudentId": 102, "StudentName": "Robert"}, {"StudentId": 103, "StudentName": "David"} ]); { "acknowledged": true, "insertedIds": ...
Read MoreHow to get specific data in different formats with MongoDB?
MongoDB provides different formatting options to retrieve and display data from collections. You can use find() for basic queries and pretty() for formatted output display. Syntax // Basic query db.collection.find(query) // Formatted output db.collection.find(query).pretty() // With limit db.collection.find(query).limit(number) Sample Data db.getSpecificData.insertMany([ { "StudentName": "John", "Information": { "FatherName": "Chris", ...
Read MoreMongoDB - How to copy rows into a newly created collection?
To copy rows from one collection to a newly created collection in MongoDB, use the aggregation pipeline with the $out operator. This operator writes the aggregation results to a specified collection. Syntax db.sourceCollection.aggregate([ { $match: {} }, { $out: "destinationCollection" } ]); Sample Data Let us first create a source collection with employee documents ? db.sourceCollection.insertMany([ {"EmployeeName": "Robert", "EmployeeSalary": 15000}, {"EmployeeName": "David", "EmployeeSalary": 25000}, {"EmployeeName": "Mike", "EmployeeSalary": 29000} ]); ...
Read MoreReplace value with a string literal during MongoDB aggregation operation
Use MongoDB $literal operator in aggregation pipelines to replace field values with fixed string constants during projection operations. The $literal operator treats its value as a literal value, preventing MongoDB from interpreting it as a field reference or expression. Syntax db.collection.aggregate([ { $project: { fieldName: { $literal: "string_value" } } } ]); Sample Data Let us first create ...
Read MoreHow to count and sum a field between 2 dates in MongoDB?
To count and sum a field between 2 dates in MongoDB, use the aggregation pipeline with $match to filter documents by date range using $gte and $lte, then $group with $sum to calculate totals. Syntax db.collection.aggregate([ { $match: { dateField: { $gte: ISODate("start-date"), ...
Read MoreBuild index in the background with MongoDB
To create index in the background, use createIndex() method and set "background: true" as the second parameter. Background indexing allows MongoDB to build indexes without blocking database operations. Syntax db.collectionName.createIndex( {"fieldName1": 1, "fieldName2": 1}, {background: true} ); Example Let us create a compound index on StudentName and StudentAge fields in the background ? db.indexCreationDemo.createIndex( {"StudentName": 1, "StudentAge": 1}, {background: true} ); { "createdCollectionAutomatically": true, "numIndexesBefore": ...
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