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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to use save() correctly in MongoDB?
The save() method in MongoDB is used to insert a new document or update an existing document based on whether the document contains an _id field. If no _id is provided, it inserts a new document. If an _id exists, it updates the existing document. Syntax db.collection.save(document) Create Sample Data Let us create a collection with documents using save() ? db.demo481.save({"FirstName":"Chris", "LastName":"Brown"}); db.demo481.save({"FirstName":"David", "LastName":"Miller"}); db.demo481.save({"FirstName":"John", "LastName":"Doe"}); db.demo481.save({"FirstName":"John", "LastName":"Smith"}); WriteResult({ "nInserted" : 1 }) WriteResult({ "nInserted" : 1 }) WriteResult({ "nInserted" : 1 }) WriteResult({ "nInserted" : 1 }) ...
Read MoreFormat date value in MongoDB shell?
To format date values in MongoDB shell, use the $dateToString operator within an aggregation pipeline. This operator converts ISODate values into custom formatted strings according to your specified format pattern. Syntax { "$dateToString": { "format": "formatString", "date": "$dateField" } } Sample Data db.demo480.insertMany([ { "id": 1, "DueDate": new ISODate("2020-01-10") }, { "id": 1, "DueDate": new ISODate("2017-12-21") }, ...
Read MoreMongoDB query to add timestamp only if it is not present
To add a timestamp field only if it is not already present in MongoDB documents, use the $exists operator with update() and set multi: true to update multiple documents at once. Syntax db.collection.update( { "fieldName": { $exists: false } }, { $set: { "fieldName": new Date() } }, { multi: true } ); Sample Data db.demo479.insertMany([ { "DueDate": ISODate("2020-01-10"), "Name": "Chris" }, { "Name": "David" }, { "DueDate": ISODate("2019-12-31"), ...
Read MoreMongoDB $unwind to get the count
The $unwind operator in MongoDB deconstructs an array field from input documents to output a separate document for each array element. Use $unwind with $group and $count in an aggregation pipeline to get counts of array elements. Syntax db.collection.aggregate([ { $unwind: "$arrayField" }, { $group: { _id: "$groupField", count: { $sum: 1 } } } ]); Sample Data db.demo478.insertMany([ { "Details": { ...
Read MoreGet the real document BSON size in MongoDB?
You can use Object.bsonsize() to get the real document BSON size in MongoDB. This method prints the BSON size of a document in bytes, which is useful for understanding storage requirements and optimizing document structure. Syntax Object.bsonsize(document) Sample Data Let us create a collection with documents ? db.demo477.insertMany([ {"ClientId": 1, "ClientName": "Chris"}, {"ClientId": 2, "ClientName": "David"}, {"ClientId": 3, "ClientName": "Bob"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreMongoDB query to update all documents matching specific IDs
To update all documents matching specific IDs in MongoDB, use updateMany() with the $in operator to specify multiple ID values in the filter criteria. Syntax db.collection.updateMany( { _id: { $in: [id1, id2, id3] } }, { $set: { field: "newValue" } } ); Sample Data db.demo476.insertMany([ { _id: 1, "Name": "Chris" }, { _id: 2, "Name": "David" }, { _id: 3, "Name": "Bob" }, { _id: 4, "Name": "Carol" ...
Read MoreMongoDB query to check the existence of multiple fields
To check the existence of multiple fields in MongoDB, use the $exists operator combined with $and. This query returns documents that contain all specified fields. Syntax db.collection.find({ $and: [ { "field1": { $exists: true } }, { "field2": { $exists: true } }, { "field3": { $exists: true } } ] }); Sample Data db.demo475.insertMany([ { "StudentFirstName": ...
Read MoreMongoDB function to return a specific data/value?
To return a specific data/value in MongoDB, use the findOne() method. The findOne() method returns the first document that satisfies the specified query criteria from the collection. Syntax db.collection.findOne(query, projection) Create Sample Data Let us create a collection with documents ? db.demo473.insertMany([ { "_id": ObjectId(), "Name": "Chris", "details": { "X-Coordinate": 10, ...
Read MoreFinding documents in MongoDB collection where a field is equal to given integer value?
To find documents where a field is equal to a given integer value, use the find() method with the field name and integer value in the query condition. Syntax db.collection.find({"fieldName": integerValue}); Sample Data Let us create a collection with documents − db.demo472.insertMany([ {"Project_Id": -101, "ProjectName": "Online Customer Tracking"}, {"Project_Id": 101, "ProjectName": "Online Banking System"}, {"Project_Id": 102, "ProjectName": "Online Library System"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreHow to remove primary key from MongoDB?
To remove the primary key (_id field) from query results in MongoDB, use projection with the _id: 0 option in the find() method. This excludes the _id field from the returned documents without deleting it from the database. Syntax db.collection.find({}, {_id: 0}); db.collection.find({}, {_id: 0, field1: 1, field2: 1}); Sample Data db.demo471.insertMany([ {"ClientId": 101, "ClientName": "Chris"}, {"ClientId": 102, "ClientName": "Bob"}, {"ClientId": 103, "ClientName": "David"} ]); { "acknowledged": true, "insertedIds": [ ...
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