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Articles on Trending Technologies
Technical articles with clear explanations and examples
Update values in multiple documents with multi parameter in MongoDB?
To update values in multiple documents in MongoDB, use the multi: true parameter in the update operation. By default, MongoDB updates only the first matching document, but setting multi: true updates all documents that match the query criteria. Syntax db.collection.update( { query }, { $set: { field: "newValue" } }, { multi: true } ); Sample Data Let us create a collection with sample documents ? db.demo390.insertMany([ { "FirstName": "Chris" }, { ...
Read MoreExtract all the values and display in a single line with MongoDB
To extract all values from nested arrays and display them in a single line in MongoDB, use the $unwind operator to flatten arrays and $group with $push to combine all values into one array. Syntax db.collection.aggregate([ { $unwind: "$arrayField" }, { $unwind: "$arrayField.nestedArray" }, { $group: { _id: null, result: { $push: "$arrayField.nestedArray" } } } ]); Sample Data db.demo389.insertOne({ "details": [ { "Name": ["Chris", "David"] }, ...
Read MoreMongoDB query to remove element from array as sub property
To remove an element from an array that exists as a sub-property in MongoDB, use the $pull operator with dot notation to target the nested array field. Syntax db.collection.update( { "matchField": "matchValue" }, { "$pull": { "parentField.arrayField": { "field": "valueToRemove" } } } ); Sample Data Let us first create a collection with documents ? db.demo388.insertOne({ _id: '101', userDetails: { isMarried: false, ...
Read MoreMongoDB query to unwind two arrays
To unwind two arrays in MongoDB, use multiple $unwind stages in an aggregation pipeline. This deconstructs each array field to create separate documents for every combination of array elements. Syntax db.collection.aggregate([ { "$unwind": "$arrayField1" }, { "$unwind": "$arrayField2" }, { "$match": { /* optional filtering */ } } ]) Sample Data db.demo387.insertOne({ "Name": "101", "Details1": [ {Value: 100, Value1: 50, Value2: 40}, ...
Read MoreConvert date parts to date in MongoDB
To convert separate date parts (year, month, day) into a complete date in MongoDB, use the $dateFromParts operator within an aggregation pipeline. This operator combines individual date components into a proper date object. Syntax db.collection.aggregate([ { $project: { dateField: { $dateFromParts: { ...
Read MoreUpdate multiple elements in an array in MongoDB?
To update multiple elements in an array in MongoDB, use the $[] all positional operator. This operator modifies all elements in the specified array field that match the update criteria. Syntax db.collection.update( { "matchCondition": "value" }, { $set: { "arrayField.$[]": "newValue" } } ); Sample Data Let us first create a collection with documents ? db.demo385.insertOne({ "ServerLogs": [ { "status": ...
Read MoreDisplay 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": { ...
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