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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to update a MongoDB document without overwriting the existing one?
To update only a field value in MongoDB, use update() along with $set. This won't overwrite the existing document but only modifies the specified fields. Syntax db.collection.update( { "field": "matchValue" }, { $set: { "fieldToUpdate": "newValue" } } ); Sample Data Let us first create a collection with documents ? db.demo401.insertOne({ "_id": 1001, "Name": "Chris", "SubjectName": "MongoDB", "Score": 45 }); { "acknowledged": true, "insertedId": 1001 ...
Read MoreMongoDB query to update only a single item from voting (up and down) records?
To update a single field in MongoDB voting records, use the $inc operator to increment or decrement vote counts. This allows you to modify only the TotalVote field without affecting other document properties. Syntax db.collection.update( { "field": "matchValue" }, { $inc: { "fieldToUpdate": incrementValue } } ); Create Sample Data Let us first create a collection with voting records − db.demo57.insertMany([ { "Votes": { "VoterName": "Chris", "TotalVote": 50 } }, { "Votes": { "VoterName": "David", "TotalVote": ...
Read MoreHow to copy attributes in MongoDB?
To copy the value of one attribute to another in MongoDB, use $set with forEach() to iterate through documents and update each one by copying the source field value to the target field. Syntax db.collection.find({}).forEach(function(doc) { db.collection.update( { _id: doc._id }, { $set: { targetField: doc.sourceField } } ); }); Sample Data db.demo55.insertMany([ { "ShippingDate": "", "date": new ISODate("2019-01-21") }, ...
Read MoreSet MongoDB $slice with a range?
To set slice with a range in MongoDB, use the $slice operator with two parameters: the starting position and the number of elements to return. This allows you to extract a specific range of elements from an array field. Syntax db.collection.find( {}, { "arrayField": { $slice: [startIndex, numberOfElements] } } ); Sample Data Let us create a collection with documents ? db.demo54.insertOne({ "ListOfValues": [100, 2030, 5353, 7364, 635, 535, 524, 423, 2434, 1323, 799874, 90] }); { ...
Read MoreMongoDB query to convert an array to a map of documents with n attributes?
To convert an array to a map of documents with n attributes in MongoDB, use the $arrayToObject operator combined with $map. This transforms array elements into key-value pairs where each document becomes a property of the resulting object. Syntax db.collection.aggregate([ { "$addFields": { "fieldName": { "$arrayToObject": { ...
Read MoreHow do I index "or" in MongoDB for indexing multiple fields?
To index multiple fields in MongoDB, use createIndex() (or the deprecated ensureIndex()) with a combination of fields. This creates compound indexes that can efficiently support queries on multiple field combinations. Syntax db.collection.createIndex({ "field1": 1, "field2": 1, "field3": -1 }); Where 1 indicates ascending order and -1 indicates descending order. Create Sample Data First, let's insert sample documents into the collection ? db.demo53.insertMany([ {"StudentFirstName": "Chris", "StudentAge": 21, "StudentCountryName": "US"}, {"StudentFirstName": "David", "StudentAge": ...
Read MoreSet a similar name from another column in MongoDB?
To copy the value from one column to another column in MongoDB, use the forEach() method to iterate through documents and update each one individually. This approach is useful when you need to set values from an existing field. Syntax db.collection.find().forEach(function(doc) { doc.targetField = doc.sourceField; db.collection.save(doc); }); Sample Data First, let's create a collection with sample documents ? db.demo51.insertMany([ {"Name1": "Chris", "Name": "David", "Age": 24}, {"Name1": "Carol", "Name": "Mike", "Age": 22}, {"Name1": ...
Read MoreHow do I get a value array (instead a json array) greater than 50 in MongoDB?
To get a value array (instead of a JSON array) for documents with values greater than 50 in MongoDB, use the distinct() method combined with $gt operator and $in for filtering. Syntax // Get distinct values greater than threshold listOfValues = db.collection.distinct("fieldName", {fieldName: {$gt: value}}); // Use $in to find documents with those values db.collection.find({fieldName: {$in: listOfValues}}); Sample Data db.demo50.insertMany([ {"Value": 40}, {"Value": 100}, {"Value": 20}, {"Value": 510} ]); { "acknowledged": ...
Read MoreSearching for an array entry via its id in a MongoDB collection and performing update
To search for an array entry via its ID in a MongoDB collection and perform an update, use the positional $ operator along with dot notation. The $ operator identifies the matched array element, allowing you to update specific fields within that element. Syntax db.collection.update( { "arrayField._id": "targetId" }, { $set: { "arrayField.$.fieldToUpdate": "newValue" } } ); Create Sample Data db.demo49.insertOne({ "Name": "David", "Details": [ { ...
Read MoreHow to return the position of a document relative to the collection in MongoDB?
To return the position of a document relative to the collection in MongoDB, use sort() along with count() to count how many documents come before the target document in sorted order. Syntax db.collection.find({field: {$lt: "targetValue"}}).sort({field: 1}).count(); Sample Data db.demo47.insertMany([ {"ClientName": "Adam"}, {"ClientName": "John"}, {"ClientName": "Chris"}, {"ClientName": "Sam"} ]); { "acknowledged": true, "insertedIds": [ ObjectId("5e267240cfb11e5c34d898f0"), ...
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