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Big Data Analytics Articles
Page 43 of 135
Get execution stats in MongoDB for a collection
To get execution stats in MongoDB for a collection, use the explain() method with "executionStats" parameter. This provides detailed performance information about query execution including execution time and documents examined. Syntax db.collection.find(query).explain("executionStats"); Sample Data db.demo157.insertMany([ {"Status": "Active"}, {"Status": "InActive"} ]); { "acknowledged": true, "insertedIds": [ ObjectId("5e354fdffdf09dd6d08539fc"), ObjectId("5e354fe3fdf09dd6d08539fd") ] } Display all documents ...
Read MoreHow to sort by the difference in array contents in MongoDB?
To sort by the difference in array contents, use MongoDB's aggregation pipeline with $project to calculate differences and $sort to order results. This is useful when comparing values between array elements. Syntax db.collection.aggregate([ { $project: { "fieldName": "$fieldName", "difference": { $subtract: [ { $arrayElemAt: ["$arrayField", index1] }, ...
Read MoreQuery a nested field within an array with MongoDB
To query a nested field within an array in MongoDB, use the $elemMatch operator to match documents where at least one array element satisfies all specified query criteria. Syntax db.collection.find({ "arrayField": { "$elemMatch": { "nestedField": "value" } } }); Sample Data Let us create a collection with documents containing nested arrays ? ...
Read MoreMongoDB query to update an array using FindAndUpdate()?
To update an array in MongoDB, use the findAndModify() method combined with the $ positional operator to target specific array elements. This method updates the document and returns either the original or updated version. Syntax db.collection.findAndModify({ query: { "arrayField": "matchValue" }, update: { $set: { "arrayField.$": "newValue" } } }); Sample Data db.demo152.insertMany([ {"id": 102, "Name": ["Chris", "David"], "Score": 45}, {"id": 103, "Name": ["Mike", "Carol"], "Score": 65} ]); { "acknowledged": ...
Read MoreMongoDB projection result as an array of selected items?
In MongoDB, projection results as an array of selected items can be achieved using the distinct() method. This method returns an array of distinct values for a specified field from documents that match the given query criteria. Syntax db.collection.distinct(field, query) Where field is the field to return distinct values from, and query is the optional filter criteria. Sample Data Let us create a collection with documents: db.demo151.insertMany([ {"ListOfNames": ["Chris", "David", "Mike"]}, {"ListOfNames": ["Mike", "Bob"]}, {"ListOfNames": ["John", "David", "Chris"]} ]); ...
Read MoreConditional update depending on field matched in MongoDB
To perform a conditional update in MongoDB, use the update() method with a query condition that matches specific field values, then apply $set to modify the target field. Only documents matching the condition will be updated. Syntax db.collection.update( { "fieldName": "matchValue" }, { $set: { "targetField": "newValue" } } ); Sample Data db.demo150.insertMany([ { "StudentId": 101, "StudentName": "Chris", "StudentMarks": 35 }, { "StudentId": 102, "StudentName": "Chris", "StudentMarks": 55 }, { "StudentId": 103, "StudentName": ...
Read MoreMongoDB $elemMatch to match document
The $elemMatch operator in MongoDB matches documents that contain an array field with at least one element matching all specified query criteria. It's particularly useful when working with arrays of embedded documents. Syntax db.collection.find( { arrayField: { $elemMatch: { field1: value1, field2: value2 } } } ); Sample Data Let us create a collection with documents − db.demo313.insertMany([ { "_id": 100, "details": [{ "Name": "Chris", "Age": 24 }] }, { "_id": 101, "details": [{ "Name": "David", "Age": 22 }] }, ...
Read MoreMongoDB - update partial number of documents?
To update multiple documents in MongoDB, use the multi: true option in the update() method. By default, MongoDB updates only the first matching document. Syntax db.collection.update( { "field": "matchValue" }, { $set: { "field": "newValue" } }, { multi: true } ); Sample Data db.demo312.insertMany([ { "FirstName": "Robert" }, { "FirstName": "Bob" }, { "FirstName": "Robert" }, { "FirstName": "David" }, ...
Read MoreGet the count of a specific value in MongoDB quickly
To get the count of a specific value in MongoDB quickly, use the countDocuments() method with a query filter. For optimal performance, create an index on the field you're counting. Syntax db.collection.countDocuments({"field": "value"}); Create Index for Performance First, create an index on the Name field for faster counting ? db.demo311.createIndex({"Name": 1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } Sample Data db.demo311.insertMany([ ...
Read MoreRetrieving a Subset of Fields from MongoDB
To retrieve a subset of fields from MongoDB documents, use field projection in the find() method. You can specify which fields to include (1) or exclude (0) from the results using dot notation for nested fields. Syntax db.collection.find( { query }, { "field1": 1, "field2": 0, "nested.field": 1 } ); Sample Data db.demo307.insertMany([ { "ClientId": 101, "ClientDetails": { "ClientFirstName": "Chris", "Age": 34 }, ...
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