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Articles by Anvi Jain
Page 9 of 43
Calculate the average value in a MongoDB document grouping by null?
To calculate the average value across all documents in a MongoDB collection, use the $group operator with _id: null to group all documents together, then apply the $avg accumulator operator. Syntax db.collectionName.aggregate([ { $group: { _id: null, "averageFieldName": { $avg: "$fieldName" } } } ]); Sample Data ...
Read MoreHow do I push elements to an existing array in MongoDB?
To push elements to an existing array in MongoDB, use the $addToSet or $push operators with the update() method. The $addToSet adds elements only if they don't already exist, while $push always adds elements regardless of duplicates. Syntax // Using $addToSet (prevents duplicates) db.collection.update( {query}, { $addToSet: { "arrayField": "newElement" } } ); // Using $push (allows duplicates) db.collection.update( {query}, { $push: { "arrayField": "newElement" } } ); Sample Data Let us create a collection with a ...
Read MoreHow to add a field with static value to MongoDB find query?
To add a field with static value to MongoDB find query, use the $literal operator with the aggregation framework. The $literal operator returns a value without parsing, making it perfect for adding constant values to query results. Syntax db.collection.aggregate([ { $project: { field1: 1, field2: 1, "staticFieldName": { $literal: ...
Read MoreUpdate array in MongoDB document by variable index?
To update array in MongoDB document by variable index, use a JavaScript variable to dynamically construct the field path. This allows you to target specific array positions using a variable instead of hardcoding the index value. Syntax var indexVariable = yourIndexValue, updateObject = { "$set": {} }; updateObject["$set"]["arrayFieldName." + indexVariable] = "newValue"; db.collectionName.update({ "_id": ObjectId("...") }, updateObject); Sample Data Let us first create a collection with documents ? db.updateByVariableDemo.insertOne({ "StudentSubjects": ["MySQL", "Java", "SQL Server", "PL/SQL"] }); { ...
Read MoreMongoDB divide aggregation operator?
The $divide operator in MongoDB performs division between two numbers during aggregation. It takes an array of exactly two numeric expressions and returns the result of dividing the first by the second. Syntax { $divide: [ , ] } Sample Data Let us first create a collection with documents ? db.aggregationOperatorDemo.insertOne({ "FirstValue": 392883, "SecondValue": 10000000000 }); { "acknowledged": true, "insertedId": ObjectId("5cd541452cba06f46efe9f01") } Following is the query to display all documents ...
Read MoreHow to pull even numbers from an array in MongoDB?
To pull even numbers from an array in MongoDB, use the $pull operator combined with the $mod operator. The $mod operator performs modulo division to identify even numbers (remainder 0 when divided by 2). Syntax db.collection.updateMany( {}, { $pull: { "arrayField": { $mod: [2, 0] } } } ); Sample Data db.pullEvenNumbersDemo.insertOne({ "AllNumbers": [101, 102, 104, 106, 108, 109, 110, 112, 14, 17, 18, 21] }); { "acknowledged": true, "insertedId": ...
Read MoreMatch element in array of MongoDB?
To match elements in arrays in MongoDB, you can use the $or operator to search for documents where any array element matches one or more conditions. This approach is useful when you want to find documents containing arrays with specific field values. Syntax db.collection.find({ $or: [ {"arrayField.subfield1": "value1"}, {"arrayField.subfield2": "value2"} ] }).limit(1); Sample Data db.matchElementInArrayDemo.insertMany([ { "StudentName": ...
Read MoreQuery to retrieve multiple items in an array in MongoDB?
To retrieve multiple items in an array in MongoDB, use the aggregation framework with $unwind, $match, and $group operators to filter and reconstruct array elements based on specific criteria. Syntax db.collection.aggregate([ { $unwind: "$arrayField" }, { $match: { "arrayField.field": { $in: [values] } } }, { $group: { "_id": "$_id", "arrayField": { $push: "$arrayField" } } } ]); Sample Data db.retrieveMultipleDemo.insertOne({ "UserDetails": [ { "_id": "101", "UserName": "John", "UserAge": ...
Read MoreFind all documents that have two specific id's in an array of objects in MongoDB?
To find all documents that have two specific id's in an array of objects in MongoDB, use the $and operator with dot notation to match multiple values within the same array field. Syntax db.collection.find({ $and: [ { "arrayField.property": value1 }, { "arrayField.property": value2 } ] }); Sample Data db.twoSpecificIdsDemo.insertMany([ { PlayerId: 1, ...
Read MoreHow to define aliases in the MongoDB Shell?
To define aliases in the MongoDB shell, you can create shortcuts for frequently used functions or expressions using Object.defineProperty(). This allows you to create reusable commands with custom names. Syntax Object.defineProperty(this, 'yourFunctionName', { get: function() { // your statements here return someValue; }, enumerable: true, configurable: true }); To assign the alias to a variable: var anyAliasName = yourFunctionName; Example Let's create an alias called displayMessageDemo ...
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