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How to get all the collections from all the MongoDB databases?

Chandu yadav
Chandu yadav
Updated on 15-Mar-2026 589 Views

To get all the collections from all MongoDB databases, you need to first retrieve all databases and then iterate through each database to get their collections. Syntax // Step 1: Get all databases switchDatabaseAdmin = db.getSiblingDB("admin"); allDatabaseName = switchDatabaseAdmin.runCommand({ "listDatabases": 1 }).databases; // Step 2: Iterate through databases to get collections allDatabaseName.forEach(function(databaseName) { db = db.getSiblingDB(databaseName.name); collectionName = db.getCollectionNames(); // Process collections as needed }); Method 1: Get All Database Names First, let us get all the databases using the admin ...

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Can I get the first item in a Cursor object in MongoDB?

Ankith Reddy
Ankith Reddy
Updated on 15-Mar-2026 720 Views

Yes, you can get the first item in a cursor object in MongoDB using the findOne() method or by applying the limit(1) method to a cursor. Syntax // Method 1: Using findOne() db.collection.findOne(); db.collection.findOne({condition}); // Method 2: Using find().limit(1) db.collection.find().limit(1); Sample Data db.getFirstItemDemo.insertMany([ {"CustomerName": "Chris", "CustomerAge": 28}, {"CustomerName": "Larry", "CustomerAge": 26}, {"CustomerName": "Robert", "CustomerAge": 29}, {"CustomerName": "David", "CustomerAge": 39} ]); { "acknowledged": true, "insertedIds": [ ...

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MongoDB query to return only embedded document?

George John
George John
Updated on 15-Mar-2026 451 Views

While MongoDB doesn't return only embedded documents directly, you can use projection to return specific fields and the $elemMatch operator to filter array elements that match certain conditions. Syntax db.collection.find( { "arrayField.nestedField": { $gte: value } }, { "arrayField": { $elemMatch: { "nestedField": { $gte: value } } } } ); Sample Data db.queryToEmbeddedDocument.insertOne({ "UserName": "Larry", "PostDetails": [ { "UserMessage": "Hello", "UserLikes": 8 }, ...

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Search a string with special characters in a MongoDB document?

Chandu yadav
Chandu yadav
Updated on 15-Mar-2026 2K+ Views

To search a string with special characters in MongoDB document, you can use backslash (\) to escape the special character in a regular expression. Here, we have special character $ in our string. Syntax db.collection.find({ "fieldName": /.*\specialCharacter.*/i }); Sample Data Let us first create a collection with documents ? db.searchDocumentWithSpecialCharactersDemo.insertMany([ { "UserId": "Smith$John123", "UserFirstName": "John", "UserLastName": "Smith" ...

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Can we use NOT and AND together in MongoDB?

Arjun Thakur
Arjun Thakur
Updated on 15-Mar-2026 274 Views

Yes, we can use NOT and AND together in MongoDB. MongoDB doesn't have direct NOT and AND operators, but we achieve this using $or and $ne operators following De Morgan's law: NOT (X AND Y) = NOT X OR NOT Y. Syntax db.collection.find({ "$or": [ {"field1": {"$ne": "value1"}}, {"field2": {"$ne": "value2"}} ] }); Sample Data db.NotAndDemo.insertMany([ {"StudentName": "John", "StudentCountryName": "US"}, {"StudentName": ...

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How to remove document on the basis of _id in MongoDB?

Ankith Reddy
Ankith Reddy
Updated on 15-Mar-2026 293 Views

To remove a document based on its _id in MongoDB, use the remove() method with the ObjectId as the matching criteria. Each document has a unique _id field that serves as the primary key. Syntax db.collectionName.remove({"_id": ObjectId("yourObjectId")}); Sample Data Let us first create a collection with sample documents ? db.removeDocumentOnBasisOfId.insertMany([ {"UserName": "Larry", "UserAge": 23, "UserCountryName": "US"}, {"UserName": "Sam", "UserAge": 21, "UserCountryName": "UK"}, {"UserName": "Chris", "UserAge": 24, "UserCountryName": "US"}, {"UserName": "Robert", "UserAge": 26, "UserCountryName": "UK"}, ...

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Increment a value in a MongoDB nested object?

George John
George John
Updated on 15-Mar-2026 528 Views

To increment a value in a MongoDB nested object, use the $inc operator combined with the $ positional operator to target the specific nested element and increment its numeric value. Syntax db.collection.update( {"nestedArray.field": "matchValue"}, { $inc: { "nestedArray.$.fieldToIncrement": incrementValue } } ); Create Sample Data Let us create a collection with a document containing nested array objects ? db.incrementValueDemo.insertOne({ "StudentName": "Larry", "StudentCountryName": "US", "StudentDetails": [ ...

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Inserting the current datetime in MongoDB?

Arjun Thakur
Arjun Thakur
Updated on 15-Mar-2026 3K+ Views

To insert current datetime in MongoDB, use new Date() during insertion or $setOnInsert with upsert operations. MongoDB stores dates in ISODate format with UTC timezone. Syntax // Direct insertion db.collection.insertOne({ fieldName: new Date() }); // With upsert operation db.collection.update( { _id: value }, { $set: { field1: "value" }, $setOnInsert: { dateField: new Date() } }, { upsert: true } ); Sample Data db.addCurrentDateTimeDemo.insertMany([ { "StudentName": "John", "StudentAdmissionDate": new Date("2012-01-21") }, { ...

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How to search document in MongoDB by _id

Ankith Reddy
Ankith Reddy
Updated on 15-Mar-2026 464 Views

To search a document in MongoDB by _id, you need to use the ObjectId() function to wrap the _id value, since MongoDB stores document IDs as ObjectId objects. Syntax db.collectionName.find({"_id": ObjectId("your_object_id_here")}); Create Sample Data Let us create a collection with sample documents ? db.searchDocumentDemo.insertMany([ {"UserId": 1, "UserName": "Larry"}, {"UserId": 2, "UserName": "Mike"}, {"UserId": 3, "UserName": "David"}, {"UserId": 4, "UserName": "Chris"}, {"UserId": 5, "UserName": "Robert"}, {"UserId": 6, "UserName": "Sam"} ...

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How to create double nested array in MongoDB?

George John
George John
Updated on 15-Mar-2026 375 Views

To create a double nested array in MongoDB, use insertOne() or insertMany() with documents containing arrays of objects that themselves contain arrays. A double nested array means an array within an array structure. Syntax db.collection.insertOne({ "field1": "value1", "outerArray": [ { "innerField": "value", "innerArray": [ ...

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