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Database Articles
Page 74 of 547
MongoDB find() to operate on recursive search?
Use dot notation with find() to perform recursive search within nested arrays and embedded documents. This allows querying deep fields without complex operators. Syntax db.collection.find({"arrayName.fieldName": value}); db.collection.find({"nestedDocument.field": value}); Sample Data db.findOperationDemo.insertMany([ { "ClientDetails": [ {"ClientId": 101, "ClientName": "Chris"}, {"ClientId": 102, "ClientName": "Robert"} ] }, ...
Read MoreI want to create a new field in an already created document. How can this be done using MongoDB query?
To create a new field in an already existing MongoDB document, use the $set operator with the update() method. The $set operator adds new fields or modifies existing field values. Syntax db.collection.update( { "matchingField": "value" }, { $set: { "newFieldName": "newValue" } } ); Create Sample Data Let us first create a collection with documents − db.createFieldDemo.insertMany([ { "StudentFirstName": "John", "StudentAge": 21 }, { "StudentFirstName": "Larry", "StudentAge": 23 }, { "StudentFirstName": "Chris", ...
Read MoreHow to store MongoDB result in an array?
To store MongoDB result in an array, use the toArray() method. This converts the cursor returned by MongoDB queries into a JavaScript array that can be manipulated and accessed using array methods. Syntax var arrayVariable = db.collectionName.find().toArray(); Create Sample Data Let us first create a collection with documents ? db.mongoDbResultInArrayDemo.insertMany([ {"CustomerName": "David Miller", "CustomerAge": 24, "isMarried": false}, {"CustomerName": "Sam Williams", "CustomerAge": 46, "isMarried": true}, {"CustomerName": "Carol Taylor", "CustomerAge": 23, "isMarried": false} ]); { ...
Read MoreGet all fields names in a MongoDB collection?
To get all field names in a MongoDB collection, you can use Map-Reduce with the distinct() method. This approach extracts all unique field names across all documents in the collection. Syntax db.runCommand({ "mapreduce": "collectionName", "map": function() { for (var key in this) { emit(key, null); } }, "reduce": function(key, values) { return null; }, "out": "temp_collection" }); db.temp_collection.distinct("_id"); Sample Data Let us create a collection ...
Read MoreHow can I update all elements in an array with a prefix string?
To update all elements in an array with a prefix string in MongoDB, use forEach() combined with map() to transform each array element and $set to update the array. This approach processes each document individually and applies the prefix to all array elements. Syntax db.collection.find().forEach(function (doc) { var prefixedArray = doc.arrayField.map(function (element) { return "PREFIX" + element; }); db.collection.update( {_id: doc._id}, ...
Read MoreMongoDB query to remove array elements from a document?
Use the $pull operator to remove array elements from a MongoDB document. This operator removes all instances of a value from an existing array field. Syntax db.collection.update( { }, { $pull: { fieldName: value } }, { multi: true } ); Sample Data Let us first create a collection with documents − db.removeArrayElementsDemo.insertMany([ { "AllPlayerName": ["John", "Sam", "Carol", "David"] }, { "AllPlayerName": ["Chris", "Robert", "John", "Mike"] } ]); { ...
Read MoreCan MongoDB find() function display avoiding _id?
Yes, MongoDB find() function can display results while excluding the _id field by using projection. Set _id: 0 in the projection parameter to hide it from the output. Syntax db.collectionName.find({}, { _id: 0 }); Sample Data Let us first create a collection with sample documents ? db.excludeIdDemo.insertMany([ { "CustomerName": "Larry" }, { "CustomerName": "Chris" }, { "CustomerName": "Mike" }, { "CustomerName": "Bob" } ]); { "acknowledged": true, ...
Read MoreMongoDB query to replace value in an array?
To replace a specific value in a MongoDB array, use the $set operator combined with the $ positional operator. The positional operator identifies the array element that matches the query condition and allows you to update it. Syntax db.collection.update( { "arrayField": "valueToReplace" }, { $set: { "arrayField.$": "newValue" } } ); Sample Data db.replaceValueInArrayDemo.insertMany([ { "StudentScores": [45, 56, 78] }, { "StudentScores": [33, 90, 67] } ]); { "acknowledged": true, ...
Read MoreMongoDB regex to display records whose first five letters are uppercase?
To find MongoDB documents whose first five letters are uppercase, use the $regex operator with the pattern /^[A-Z]{5}/. The ^ ensures matching from the string beginning, and {5} specifies exactly five consecutive uppercase letters. Syntax db.collection.find({ fieldName: { $regex: /^[A-Z]{5}/ } }); Sample Data db.upperCaseFiveLetterDemo.insertMany([ { "StudentFullName": "JOHN Smith" }, { "StudentFullName": "SAM Williams" }, { "StudentFullName": "CAROL Taylor" }, { "StudentFullName": "Bob Taylor" }, { "StudentFullName": "DAVID Miller" ...
Read MoreHow to perform $gt on a hash in a MongoDB document?
The $gt operator selects documents where the value of a field is greater than a specified value. When working with embedded documents (hash/object structures), use dot notation to access nested fields within the $gt query. Syntax db.collection.find({ "parentField.nestedField": { $gt: value } }); Sample Data db.performQueryDemo.insertMany([ { "PlayerDetails": { "PlayerScore": 1000, "PlayerLevel": 2 ...
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