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Articles by AmitDiwan
Page 580 of 840
Display only a single field from all the documents in a MongoDB collection
To display only a single field from all documents in a MongoDB collection, use projection in the find() method. Set the desired field to 1 to include it, or set unwanted fields to 0 to exclude them. Syntax db.collection.find({}, {fieldName: 1, _id: 0}); // OR db.collection.find({}, {unwantedField1: 0, unwantedField2: 0}); Sample Data db.demo384.insertMany([ {"StudentName": "Chris Brown", "StudentCountryName": "US"}, {"StudentName": "David Miller", "StudentCountryName": "AUS"}, {"StudentName": "John Doe", "StudentCountryName": "UK"} ]); { "acknowledged": true, ...
Read MoreMongoDB query to filter only the logs containing the "work" word in the content
To filter logs containing the word "work" in MongoDB, use the $filter operator with $indexOfBytes to perform case-insensitive substring matching within an aggregation pipeline. Syntax db.collection.aggregate([ { "$addFields": { "arrayField": { "$filter": { "input": "$arrayField", ...
Read MoreMongoDB aggregate $slice to get the length of the array
To get the length of an array in MongoDB using aggregation, use the $size operator within a $project stage. The $size operator returns the number of elements in the specified array field. Syntax db.collection.aggregate([ { $project: { "fieldName": { $size: "$arrayField" } } } ]); Sample Data Let us create a collection with documents ? db.demo382.insertOne({ "Name": "David", "details": [ { ...
Read MoreHow to search an array for values present in another array and output the indexes of values found into a new array in MongoDB?
To search an array for values present in another array and output the indexes of values found into a new array in MongoDB, use the $indexOfArray operator combined with $map within an aggregation pipeline. Syntax db.collection.aggregate([ { "$project": { "Result": { "$map": { ...
Read MoreMongoDB $addToSet to add a deep nested array of object?
The $addToSet operator adds a value to an array unless the value is already present, in which case $addToSet does nothing to that array. When working with deep nested arrays, combine $addToSet with the positional operator $ to target specific array elements. Syntax db.collection.update( { "parentArray.field": "matchValue" }, { $addToSet: { "parentArray.$.nestedArray": newObject } } ); Sample Data Let us first create a collection with documents − db.demo380.insertOne({ "details": [ { ...
Read MoreMongoDB projection on specific nested properties?
To project specific nested properties in MongoDB, use the aggregation pipeline with $addFields, $objectToArray, $filter, and $arrayToObject operators to selectively include nested fields based on conditions. Syntax db.collection.aggregate([ { "$addFields": { "nested.path": { "$arrayToObject": { "$filter": { ...
Read MoreManipulating subdocuments in MongoDB
To manipulate subdocuments in MongoDB, use dot notation to target specific fields within embedded documents or arrays. The $ positional operator helps update elements that match query conditions. Syntax db.collection.update( { "arrayField.field": "matchValue" }, { $operation: { "arrayField.$.targetField": value } } ); Create Sample Data db.demo378.insertOne({ Name: "Chris", details: [ { id: 101, Score: 56 }, { id: 102, Score: 78 ...
Read MoreHow can I concatenate an array of integer in MongoDB aggregation method?
To concatenate an array of integers in MongoDB aggregation, use the $reduce operator with $concat to combine array elements into a single string. Since integers must be converted to strings for concatenation, use $toString for type conversion. Syntax db.collection.aggregate([ { $project: { concatenatedField: { $reduce: { ...
Read MoreHow to update after aggregate in MongoDB?
To update documents after performing aggregation analysis in MongoDB, you cannot directly update within the aggregation pipeline. Instead, use the update() method with array filters to target specific array elements based on conditions. Syntax db.collection.update( { "field": value }, { $inc: { "arrayField.$[identifier].field": incrementValue } }, { arrayFilters: [{ "identifier.field": condition }] } ); Sample Data Let us first create a collection with documents ? db.demo376.insertOne({ "id": 101, "details": [ ...
Read MoreMongoDB query to execute stored function?
JavaScript functions can be saved for reuse using a system collection called system.js. To store a function, use db.collection.save(), then execute it with db.eval(). Syntax // Store function db.system.js.save({ _id: "functionName", value: function(parameters) { // function body return result; } }); // Execute function db.eval("functionName(arguments)"); Example: Store and Execute Function Let us first create a function ? db.system.js.save({ _id: ...
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