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Articles by Smita Kapse
Page 13 of 39
Is it possible to cast in a MongoDB Query?
Yes, it is possible to cast in a MongoDB query using JavaScript expressions with the $where operator, which allows automatic type conversion from string to number for comparisons. Syntax db.collection.find("this.fieldName > value"); Sample Data Let us create a collection with sample documents containing Amount values stored as strings ? db.castingDemo.insertMany([ {"Amount": "200"}, {"Amount": "100"}, {"Amount": "110"}, {"Amount": "95"}, {"Amount": "85"}, {"Amount": "75"} ]); { ...
Read MoreMongoDB query by sub-field?
To query by subfield in MongoDB, use dot notation to access nested document fields. This allows you to search for specific values within embedded documents using the field.subfield syntax. Syntax db.collection.find({ "parentField.childField": "value" }) Sample Data Let's create sample documents with nested fields ? db.queryBySubFieldDemo.insertMany([ { "StudentPersonalDetails": { "StudentName": "John", "StudentHobby": "Photography" ...
Read MoreHow to convert ObjectId to string in MongoDB
To convert ObjectId to string in MongoDB, use the $toString operator within an aggregation pipeline. This converts the ObjectId value to its string representation. Syntax db.collection.aggregate([ { $project: { _id: { $toString: "$_id" }, // other fields as needed } } ]); Sample Data db.objectidToStringDemo.insertMany([ ...
Read MoreHow to print to console an object in a MongoDB script?
To print an object to the console in a MongoDB script, you can use the printjson() method for formatted output or print() with JSON.stringify() for compact output. Syntax // Method 1: Formatted output printjson({field1: "value1", field2: "value2"}); // Method 2: Compact output print(JSON.stringify({field1: "value1", field2: "value2"})); Method 1: Using printjson() (Formatted Output) The printjson() method displays objects with proper indentation and formatting ? printjson({ "UserId": 101, "UserName": "John", "UserCoreSubject": ["Java", "MongoDB", "MySQL", "SQL Server"] }); ...
Read MoreRemoving _id element from PyMongo results?
To remove the _id element from MongoDB query results, use projection with {'_id': false} in the find() method. This excludes the _id field from the returned documents. Syntax db.collection.find({}, {'_id': false}) Sample Data db.removingidElementDemo.insertMany([ {"UserName": "John", "UserAge": 21}, {"UserName": "Carol", "UserAge": 24}, {"UserName": "David", "UserAge": 22}, {"UserName": "Mike", "UserAge": 26}, {"UserName": "Chris", "UserAge": 20} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreIs it possible to use variable for collection name using PyMongo?
Yes, it is possible to use variables for collection names in PyMongo. You can store the collection name as a string variable and access the collection dynamically using bracket notation or the get_collection() method. Syntax # Method 1: Using bracket notation collection_name = "your_collection_name" collection = db[collection_name] # Method 2: Using get_collection() method collection = db.get_collection(collection_name) MongoDB Shell Example First, let's see how to use variables for collection names in MongoDB shell ? var storeCollectionName = "new_Collection"; db[storeCollectionName].insertMany([ {"UserName": "John", "UserAge": 21}, ...
Read MoreAvoid duplicate entries in MongoDB?
To avoid duplicate entries in MongoDB, create a unique index on the field that should have unique values. This prevents insertion of documents with duplicate values and throws an error if attempted. Syntax db.collectionName.createIndex({"fieldName": 1}, {unique: true}); Example: Create Unique Index Let's create a unique index on the UserName field to prevent duplicate usernames ? db.avoidDuplicateEntriesDemo.createIndex({"UserName": 1}, {unique: true}); { "createdCollectionAutomatically": true, "numIndexesBefore": 1, "numIndexesAfter": 2, "ok": 1 } Test with ...
Read MoreHow to get distinct list of sub-document field values in MongoDB?
To get distinct list of sub-document field values in MongoDB, use the distinct() method with dot notation to access nested fields within arrays or embedded documents. Syntax db.collection.distinct("outerField.innerField"); Sample Data Let us create a collection with student documents containing nested arrays ? db.getDistinctListOfSubDocumentFieldDemo.insertMany([ { "StudentId": 101, "StudentPersonalDetails": [ { ...
Read MoreMongoDB print JSON without whitespace i.e. unpretty JSON?
To print JSON without whitespace (unpretty JSON) in MongoDB, use the printjsononeline() function to compress documents into single-line format without pretty-print formatting. Syntax var cursor = db.collection.find().sort({_id:-1}).limit(10000); while(cursor.hasNext()) { printjsononeline(cursor.next()); } Sample Data db.unprettyJsonDemo.insertMany([ {"StudentName":"John", "StudentAge":21, "StudentTechnicalSkills":["C", "C++"]}, {"StudentName":"Carol", "StudentAge":22, "StudentTechnicalSkills":["MongoDB", "MySQL"]} ]); { "acknowledged" : true, "insertedIds" : [ ObjectId("5c900df25705caea966c557d"), ObjectId("5c900e085705caea966c557e") ...
Read MoreIn MongoDB how do you use $set to update a nested value/embedded document?
In MongoDB, use the $set operator with dot notation to update values inside nested documents (embedded documents). This allows you to modify specific fields within nested objects without replacing the entire document. Syntax db.collectionName.update( { "matchCondition": "value" }, { $set: { "outerField.innerField": "newValue" } } ); Sample Data Let us create a collection with a nested document ? db.updateNestedValueDemo.insertOne({ "CustomerName": "Chris", "CustomerDetails": { "CustomerAge": 25, ...
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