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Articles on Trending Technologies
Technical articles with clear explanations and examples
MongoDB query to get only specific fields in nested array documents?
To get only specific fields in nested array documents in MongoDB, use $filter with $project in an aggregation pipeline to match conditions and extract required data from deeply nested arrays. Syntax db.collection.aggregate([ { $project: { "field": { $filter: { ...
Read MoreMongoDB query to find value in array with multiple criteria (range)
To find values in an array within a specific range in MongoDB, use $elemMatch with $gt and $lt operators. This allows you to match documents where at least one array element satisfies multiple criteria. Syntax db.collection.find({ "arrayField": { "$elemMatch": { "field": { "$gt": minValue, ...
Read MoreMongoDB findById returning a list of documents instead of a single result? How to get only a single document?
To get only a single result instead of a list when querying by ID in MongoDB, use the findOne() method instead of find(). The findOne() method returns exactly one document that matches your query criteria. Syntax db.collection.findOne({_id: ObjectId("id_value")}) Sample Data Let us create a collection with documents − db.demo340.insertMany([ {_id: 1, "Name": "Chris", Age: 21}, {_id: 2, "Name": "David", Age: 23}, {_id: 3, "Name": "Bob", Age: 20}, {_id: 4, "Name": "Sam", Age: 19} ]); ...
Read MoreZip two arrays and create new array of object in a reshaped form with MongoDB
To zip two arrays and create a new array of objects in MongoDB, use the $zip operator within an aggregation pipeline. This combines elements from multiple arrays at corresponding positions into a single reshaped structure. Syntax db.collection.aggregate([ { $project: { "newFieldName": { $map: { ...
Read MoreWorking with MongoDB concatArrays in project on existing multi-array field
The $concatArrays operator is used to concatenate arrays and return the concatenated array. When working with multi-dimensional arrays, you can combine it with $reduce to flatten and concatenate nested arrays. Syntax { "$project": { "newFieldName": { "$reduce": { "input": "$arrayField", "initialValue": [], "in": { "$concatArrays": ["$$this", "$$value"] } } } ...
Read MoreHow to calculate sum in MongoDB with aggregate()?
To calculate sum in MongoDB, use the $sum operator along with the aggregate() method. The $sum operator is used within a $group stage to calculate the total of numeric field values across documents. Syntax db.collection.aggregate([ { $group: { _id: null, totalFieldName: { $sum: "$fieldName" } } } ]); ...
Read MoreHow to update only one property in MongoDB?
To update only one property in MongoDB, use the $set operator to modify a specific field without affecting other properties of the document. For arrays, use $addToSet or $push operators. Syntax db.collection.updateOne( { "field": "value" }, { $set: { "propertyToUpdate": "newValue" } } ); Sample Data db.demo336.insertMany([ { "Name": "Chris", "Score": [45, 67, 78] }, { "Name": "David", "Score": [89, 93, 47] } ]); { "acknowledged": true, ...
Read MoreMongoDB query to convert a string with commas to double
To convert a string with commas to a double value in MongoDB, use the aggregate pipeline with $split, $reduce, and $convert operators to remove commas and convert the result to a numeric type. Syntax db.collection.aggregate([ { $project: { convertedField: { $convert: { ...
Read MoreMongoDB query to add matched key to list after query?
To add matched elements to a list after querying in MongoDB, use the $filter operator within an aggregation pipeline. This allows you to filter array elements based on specific conditions and return only the matching elements. Syntax db.collection.aggregate([ { $addFields: { arrayField: { $filter: { ...
Read MoreCreate an index for text search in MongoDB
To create an index for text search in MongoDB, use the createIndex() method with the "text" index type. This enables full-text search capabilities on string fields using the $text operator. Syntax db.collection.createIndex({ fieldName: "text" }); db.collection.find({ $text: { $search: "searchTerm" } }); Sample Data Let us create a collection with sample documents: db.demo331.insertMany([ { "Words": "This is a MySQL" }, { "Words": "THIS is a MongoDB" } ]); { "acknowledged": true, "insertedIds": [ ...
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