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Articles on Trending Technologies
Technical articles with clear explanations and examples
Is 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 MoreGet database data size in MongoDB?
To get the database data size in MongoDB, you can use the db.stats() method. This method returns detailed statistics about the current database including data size, storage size, and other useful metrics. Syntax db.stats() Example 1: Check Current Database Statistics First, check which database you are currently using ? db test Now get the database statistics for the 'test' database ? db.stats() { "db" : "test", "collections" : 114, "views" ...
Read MoreFind a document with ObjectID in MongoDB?
To find a document with ObjectId in MongoDB, use the ObjectId() constructor in your query to match the specific _id field value. Syntax db.collectionName.find({"_id": ObjectId("yourObjectIdValue")}).pretty(); Sample Data Let us create a collection with sample documents to demonstrate finding by ObjectId ? db.findDocumentWithObjectIdDemo.insertMany([ {"UserName": "Larry"}, {"UserName": "Mike", "UserAge": 23}, {"UserName": "Carol", "UserAge": 26, "UserHobby": ["Learning", "Photography"]} ]); { "acknowledged": true, "insertedIds": [ ...
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 MoreQuerying array elements with MongoDB?
MongoDB provides simple and efficient ways to query documents that contain specific values within array fields. You can search for documents where an array contains a particular element using standard find() operations. Syntax db.collection.find({arrayFieldName: "value"}); This syntax returns all documents where the specified array field contains the given value. Sample Data Let us create a collection with sample documents to demonstrate array querying ? db.queryArrayElementsDemo.insertMany([ { "StudentName": "John", "StudentFavouriteSubject": ["C", "Java"] ...
Read MoreHow to know which storage engine is used in MongoDB?
To know which storage engine is used in MongoDB, you can use the db.serverStatus().storageEngine command. This returns basic information about the current storage engine including its name and capabilities. Syntax db.serverStatus().storageEngine; For detailed configuration statistics of the storage engine ? db.serverStatus().storageEngineName; Example 1: Check Storage Engine db.serverStatus().storageEngine; { "name" : "wiredTiger", "supportsCommittedReads" : true, "supportsSnapshotReadConcern" : true, "readOnly" : false, "persistent" : true } This output shows that WiredTiger ...
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 MorePerform aggregation sort in MongoDB?
To perform aggregation sort in MongoDB, use the aggregate() method with the $sort stage. The $sort stage orders documents by specified fields in ascending (1) or descending (-1) order. Syntax db.collection.aggregate([ { $group: { ... } }, { $sort: { field: 1 } } // 1 = ascending, -1 = descending ]); Sample Data db.aggregationSortDemo.insertMany([ {"StudentId": 98, "StudentFirstName": "John", "StudentLastName": "Smith"}, {"StudentId": 128, "StudentFirstName": "Carol", "StudentLastName": "Taylor"}, {"StudentId": 110, "StudentFirstName": ...
Read MoreSelect MongoDB documents where a field either does not exist, is null, or is false?
To select MongoDB documents where a field either does not exist, is null, or is false, use the $in operator with an array containing false and null values. MongoDB treats non-existing fields as null when querying. Syntax db.collection.find({ "fieldName": { $in: [false, null] } }); Sample Data db.selectMongoDBDocumentsWithSomeCondition.insertMany([ {"StudentId": 1, "StudentName": "Larry"}, {"StudentId": 2, "StudentName": "Mike", "hasAgeGreaterThanOrEqualTo18": true}, {"StudentId": 3, "StudentName": "Carol", "hasAgeGreaterThanOrEqualTo18": false}, {"StudentId": 4, "StudentName": "Sam", "hasAgeGreaterThanOrEqualTo18": null}, ...
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") ...
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