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Database Articles
Page 9 of 547
How to use custom variable while updating a MongoDB document?
To use custom variables while updating MongoDB documents, first declare a variable with var, then reference it in your update() operation. This allows for dynamic updates and better code reusability. Syntax var variableName = yourValue; db.collectionName.update( { filter }, { $set: { fieldName: variableName } } ); Create Sample Data db.demo600.insertMany([ { id: 1, Name: "Robert" }, { id: 2, Name: "Mike" }, { id: 3, Name: "Sam" } ]); ...
Read MoreHow to subtract values (TotalPrice – Discount) from document field values in MongoDB?
To subtract values from document field values in MongoDB, use the $subtract operator within the aggregation pipeline. This operator performs arithmetic subtraction between numeric field values or expressions. Syntax db.collection.aggregate([ { $project: { newField: { $subtract: ["$field1", "$field2"] } ...
Read MoreFind which MongoDB document contains a specific string?
To find which document contains a specific string, use $regex along with find(). The regex operator performs pattern matching to locate documents containing the specified text substring. Syntax db.collection.find({ fieldName: { $regex: /pattern/flags } }); Sample Data db.demo597.insertMany([ { "Name": "John Doe" }, { "Name": "John Smith" }, { "Name": "Chris Brown" }, { "Name": "Adam Smith" } ]); { "acknowledged": true, ...
Read MoreMongoDB query to update nested document
To update a nested document in MongoDB, use the $ positional operator with the $set operator. The $ operator identifies the array element that matches the query condition and allows you to update specific fields within that element. Syntax db.collection.update( {"arrayName.field": "matchValue"}, { $set: { "arrayName.$.field": "newValue" } } ); Create Sample Data Let us create a collection with documents − db.demo595.insertOne({ "Information": [ { "_id": new ObjectId(), "Name": "Chris" }, ...
Read MoreMongoDB query to limit the returning values of a field?
To limit the returning values of a field in MongoDB, use the $slice operator in the projection parameter of the find() method. This is particularly useful for limiting array elements returned in query results. Syntax db.collection.find( {}, { "arrayField": { "$slice": numberOfElements } } ); Sample Data db.demo594.insertOne({ id: 1, details: [ { Name: "Chris", Age: 21 }, { Name: "Bob", ...
Read MoreFetch specific multiple documents in MongoDB
To fetch specific multiple documents in MongoDB, use the $in operator to match documents where a field value equals any value in a specified array. Syntax db.collection.find({ "field": { $in: [value1, value2, value3, ...] } }); Sample Data Let us create a collection with documents − db.demo593.insertMany([ { id: 1, "Name": "Chris" }, { id: 2, "Name": "John" }, { id: 3, "Name": "Bob" }, { id: 4, "Name": "Sam" } ]); ...
Read MoreMongoDB query to match documents that contain an array field
To match documents that contain an array field, use the $elemMatch operator. This operator matches documents where at least one array element meets all specified criteria within a single element. Syntax db.collection.find({ "arrayField": { "$elemMatch": { "field1": "value1", "field2": "value2" } } }); Sample Data Let ...
Read MoreMongoDB query to find "where" Billing Address is Equal to Delivery Address from documents?
To find documents where billing address equals delivery address in MongoDB, use the $where operator with JavaScript expressions to compare field values within the same document. Syntax db.collection.find({ $where: "this.field1 == this.field2" }); Sample Data db.demo589.insertMany([ {deliveryAddress: "US", billingAddress: "UK"}, {deliveryAddress: "US", billingAddress: "US"}, {deliveryAddress: "US", billingAddress: "AUS"}, {deliveryAddress: "UK", billingAddress: "US"} ]); { "acknowledged" : true, "insertedIds" : [ ...
Read MoreMongoDB query to gather unique array item?
To gather unique array items from a MongoDB collection, use the distinct() method. This method returns an array of unique values for a specified field, automatically removing duplicates. Syntax db.collection.distinct("fieldName") Sample Data Let us create a collection with documents ? db.demo588.insertOne({ "CountryName": ["US", "AUS", "UK", "US", "UK", "AUS"] }); { "acknowledged": true, "insertedId": ObjectId("5e92bbd2fd2d90c177b5bccb") } Display all documents from the collection ? db.demo588.find().pretty(); { "_id": ObjectId("5e92bbd2fd2d90c177b5bccb"), ...
Read MoreHow to keep appending subdocuments in MongoDB?
To append subdocuments in MongoDB, use the $push operator with the update() method. This operator adds new subdocuments to an existing array field without removing existing elements. Syntax db.collection.update( { "field": "matchValue" }, { "$push": { "arrayField": { subdocumentData } } } ); Sample Data Let us create a collection with documents − db.demo587.insertMany([ { "id": 101, "details": [{ Name: "Chris", Age: 21, Marks: 57 }] }, { "id": 102, "details": [{ Name: "Bob", Age: 22, ...
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