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Big Data Analytics Articles
Page 23 of 135
How to check empty field in a MongoDB collection?
To check empty field in a MongoDB collection, use $exists along with $eq operator. The $exists ensures the field is present, while $eq matches the empty string value. Syntax db.collection.find({ "fieldName": { "$exists": true, "$eq": "" } }); Create Sample Data Let us create a collection with documents containing empty and non-empty fields ? db.demo485.insertMany([ {"FirstName": "Chris", "LastName": ""}, {"FirstName": ...
Read MoreSearch array of objects in a MongoDB collection?
To search array of objects in MongoDB, use the find() method with dot notation to target specific fields within array elements. The find() method selects documents in a collection and returns a cursor to the matched documents. Syntax db.collection.find({ "arrayField.objectProperty": "value" }); // Multiple conditions with $or db.collection.find({ $or: [ {"arrayField.property1": "value1", "arrayField.property2": "value2"}, {"arrayField.property1": "value3", "arrayField.property2": "value4"} ] }); Sample Data Let us create ...
Read MoreSet variable value in MongoDB save() method
To set a variable value in MongoDB's save() method, use db.collectionName.save(variableName) where variableName is your JavaScript variable containing the document data. Syntax var variableName = { field1: "value1", field2: "value2" }; db.collectionName.save(variableName); Example Let us create a variable with document data and save it to a collection ? Step 1: Create a Variable var Info = { "Name": "David", "CountryName": "US", "ProjectDetails": [ { ...
Read MoreFetch specific documents with array values in MongoD
To fetch specific documents with array values in MongoDB, use the limit() method combined with toArray(). The toArray() method returns an array containing all documents from a cursor, while limit() restricts the number of documents returned. Syntax db.collection.find().limit(numberOfDocuments).toArray() Create Sample Data Let us create a collection with documents containing array values ? db.demo482.insertMany([ {_id:1, "StudentInformation":[{"Name":"Chris", "Age":21}]}, {_id:2, "StudentInformation":[{"Name":"Bob", "Age":23}]}, {_id:3, "StudentInformation":[{"Name":"David", "Age":20}]} ]); { "acknowledged" : true, "insertedIds" : ...
Read MoreHow 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" ...
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