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Articles on Trending Technologies
Technical articles with clear explanations and examples
Query array of nested string with MongoDB?
To query array of nested string in MongoDB, you can use dot notation to access nested array elements. This allows you to search for specific string values within arrays that are nested inside other objects. Syntax db.collection.find({"parentField.nestedArrayField": "searchValue"}) Sample Data Let us first create a collection with documents containing nested arrays of strings ? db.nestedStringDemo.insertMany([ { "CustomerName": "John", "CustomerOtherDetails": [ ...
Read MoreReplace an array field value with MongoDB?
To replace an array field value in MongoDB, use the $ positional operator with $set. The positional operator identifies the array element that matches the query condition and replaces it with the new value. Syntax db.collection.update( { "arrayField": "valueToReplace" }, { $set: { "arrayField.$": "newValue" } } ); Sample Data db.replaceAnArrayFieldValueDemo.insertOne({ "StudentTechnicalSubjects": ["MySQL", "SQL Server", "PL/SQL"] }); { "acknowledged": true, "insertedId": ObjectId("5cea41e0ef71edecf6a1f68f") } View Current Document ...
Read MoreFilter by several array elements in MongoDB?
To filter documents by several array elements in MongoDB, use the $elemMatch operator. This operator matches documents containing an array field with at least one element that satisfies all specified query criteria. Syntax db.collection.find({ arrayField: { $elemMatch: { field1: "value1", field2: "value2" } } }); Sample Data ...
Read MoreMongoDB. max length of field name?
MongoDB supports the BSON format data and has no explicit maximum length limit for field names. However, the practical limit is constrained by the overall BSON document size limit of 16MB. Syntax db.collection.insertOne({ "fieldNameOfAnyLength": "value" }); Example: Inserting Document with Very Long Field Name Let us create a collection with a document containing an extremely long field name ? db.maxLengthDemo.insertOne({ "maxLengthhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh": "This is demo" }); { "acknowledged": true, "insertedId": ObjectId("5ce97ac978f00858fb12e926") } ...
Read MoreUpdate a single list item of a MongoDB document?
To update a single list item in MongoDB, use the positional operator ($) to target the first array element that matches your query condition. This operator allows you to update specific fields within array elements without affecting other items in the list. Syntax db.collection.update( { "arrayField.field": "matchValue" }, { $set: { "arrayField.$.field": "newValue" } } ); Sample Data Let us first create a collection with documents ? db.updateASingleListDemo.insertOne({ _id: 1, "EmployeeName": "Chris", ...
Read MoreRetrieving array values from a find query in MongoDB?
To retrieve array values from a MongoDB find query, use dot notation to access array fields and their nested properties. This allows you to query specific elements within arrays and filter documents based on array content. Syntax db.collection.find({"arrayField.nestedProperty": "value"}); Sample Data db.retrievingArrayDemo.insertMany([ { "UserDetails": [ { "UserName": "John", "UserAge": 23 } ], "UserCountryName": ...
Read MoreConvert a field to an array using MongoDB update operation?
To convert a field to an array in MongoDB, use the $set operator to replace the existing field value with an array containing that value. This is useful when you need to transform single values into arrays for future operations. Syntax db.collection.update( { _id: ObjectId("id") }, { $set: { "fieldName": [existingValue] } } ) Sample Data Let us first create a collection with a document having a string field ? db.convertAFieldToAnArrayDemo.insertOne({ "StudentSubject": "MongoDB" }); { ...
Read MoreRemoving empty fields from MongoDB
To remove empty fields from MongoDB documents, use updateMany() with the $unset operator. This operation identifies documents with empty string values and removes those fields entirely. Syntax db.collection.updateMany( { "fieldName": "" }, { $unset: { "fieldName": 1 } } ); Sample Data Let us create a collection with documents containing empty fields ? db.removeEmptyFieldsDemo.insertMany([ { "StudentName": "" }, { "StudentName": "Chris" }, { "StudentName": "" }, { "StudentName": ...
Read MoreCreating an index on a nested MongoDB field?
To create an index on a nested MongoDB field, use dot notation to specify the path to the nested field within the createIndex() method. This improves query performance when searching or sorting by nested field values. Syntax db.collection.createIndex({ "parentField.nestedField.deepField": 1 }) Where 1 indicates ascending order and -1 indicates descending order. Sample Data Let us create a collection with nested documents ? db.createIndexOnNestedFieldDemo.insertMany([ { "UserDetails": { "UserPersonalDetails": ...
Read MoreFind documents where all elements of an array have a specific value in MongoDB?
To find documents where all elements of an array have a specific value in MongoDB, use the $not operator with $elemMatch to exclude documents that contain any element NOT matching the desired value. Syntax db.collection.find({ "arrayField": { $not: { $elemMatch: { "field": { $ne: "specificValue" } ...
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