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Articles by Nishtha Thakur
Page 9 of 40
Is there a way to limit the number of records in a certain MongoDB collection?
Yes, you can limit the number of records in a MongoDB collection by creating a capped collection. Capped collections maintain insertion order and automatically remove the oldest documents when the collection reaches its maximum size or document limit. Syntax db.createCollection("collectionName", { capped: true, size: sizeInBytes, max: maxDocuments }); Example: Create Collection with Document Limit Let us create a collection that can hold a maximum of 3 documents ? db.createCollection("limitTheNumberOfRecordsDemo", { capped: true, ...
Read MoreMongoDB 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 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 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 ...
Read MoreHow can I drop a collection in MongoDB with two dashes in the name?
To drop a collection in MongoDB that has special characters like two dashes in its name, you need to use the getCollection() method instead of direct dot notation, since MongoDB cannot parse collection names with special characters using standard syntax. Syntax db.getCollection("collectionNameWithSpecialCharacters").drop(); Create Sample Collection First, let's create a collection with two dashes in the name ? db.createCollection("company--EmployeeInformation"); { "ok" : 1 } Insert Sample Data Add some documents to the collection ? db.getCollection("company--EmployeeInformation").insertMany([ {"CompanyName": "Amazon", "EmployeeName": "Chris"}, ...
Read MoreDecrement only a single value in MongoDB?
To decrement only a single value in MongoDB, use the $inc operator with a negative value. This allows you to decrease a numeric field by a specified amount while targeting only one document. Syntax db.collection.update( { field: "matchValue" }, { $inc: { numericField: -decrementValue } } ); Create Sample Data db.decrementingOperationDemo.insertMany([ { "ProductName": "Product-1", "ProductPrice": 756 }, { "ProductName": "Product-2", "ProductPrice": 890 }, { "ProductName": "Product-3", "ProductPrice": 994 }, ...
Read MoreConcatenate fields in MongoDB?
To concatenate fields in MongoDB, use the $concat operator within an aggregation pipeline. This operator combines multiple string values into a single string, with optional separators between them. Syntax db.collection.aggregate([ { $project: { "newField": { $concat: ["$field1", "separator", "$field2"] } ...
Read MoreUpdate multiple rows in a single MongoDB query?
To update multiple rows in a single MongoDB query, use bulk operations with initializeUnorderedBulkOp() method. This allows you to batch multiple update operations together and execute them as one atomic operation. Syntax var bulkOp = db.collection.initializeUnorderedBulkOp(); bulkOp.find({condition1}).updateOne({$set: {field: "value"}}); bulkOp.find({condition2}).updateOne({$set: {field: "value"}}); bulkOp.execute(); Sample Data db.upDateMultipleRowsDemo.insertMany([ {"CustomerName": "John", "CustomerPurchaseAmount": 500}, {"CustomerName": "Chris", "CustomerPurchaseAmount": 700}, {"CustomerName": "David", "CustomerPurchaseAmount": 50}, {"CustomerName": "Larry", "CustomerPurchaseAmount": 1900} ]); { "acknowledged": true, ...
Read MoreGetting a list of values by using MongoDB $group?
To get a list of values using MongoDB, use the $group aggregation stage along with the $push operator. This approach groups documents by a specific field and creates an array of values from another field. Syntax db.collection.aggregate([ { $group: { _id: "$groupingField", arrayField: { $push: "$fieldToCollect" } } } ...
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