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MongoDB Articles
Page 100 of 111
How to retrieve a value from MongoDB by its key name?
To retrieve a value from MongoDB by its key name, use projection in the find() method to specify which fields to return while excluding others. Syntax db.collectionName.find({}, {"fieldName": 1}); Set the field value to 1 to include it, or 0 to exclude it from the result. Sample Data db.retrieveValueFromAKeyDemo.insertMany([ {"CustomerName": "Larry", "CustomerAge": 21, "CustomerCountryName": "US"}, {"CustomerName": "Chris", "CustomerAge": 24, "CustomerCountryName": "AUS"}, {"CustomerName": "Mike", "CustomerAge": 26, "CustomerCountryName": "UK"} ]); { "acknowledged": true, ...
Read MoreDelete a collection from MongoDB with special characters?
To delete a MongoDB collection that contains special characters in its name (like underscore _ or hyphen -), use the getCollection() method followed by drop(). Syntax db.getCollection("collectionNameWithSpecialChars").drop(); Create Sample Data Let us create a collection with special characters and add some documents ? db.createCollection("_personalInformation"); { "ok" : 1 } db.getCollection('_personalInformation').insertMany([ {"ClientName":"Chris", "ClientCountryName":"US"}, {"ClientName":"Mike", "ClientCountryName":"UK"}, {"ClientName":"David", "ClientCountryName":"AUS"} ]); { "acknowledged" : true, "insertedIds" : ...
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 MoreHow to count number of keys in a MongoDB document?
There is no built-in function to count the number of keys in a MongoDB document. You need to write JavaScript code in the MongoDB shell to iterate through the document and count its fields. Syntax myDocument = db.collection.findOne({}); numberOfKeys = 0; for(key in myDocument) { numberOfKeys++; } print("Total keys: " + numberOfKeys); Sample Data Let us create a collection with a document ? db.numberofKeysInADocumentDemo.insertOne({ "UserName": "John", "UserAge": 21, "UserEmailId": "john12@gmail.com", "UserCountryName": "US" }); ...
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 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 ...
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