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Big Data Analytics Articles
Page 35 of 135
MongoDB query to convert string to int?
To convert string to int in MongoDB, you can use parseInt() with forEach() for iteration or the $toInt operator for aggregation pipelines. The forEach() method allows you to iterate through documents and modify field types. Syntax // Method 1: Using forEach() with parseInt() db.collection.find().forEach(function(doc) { doc.fieldName = parseInt(doc.fieldName); db.collection.save(doc); }); // Method 2: Using $toInt in aggregation db.collection.aggregate([ { $addFields: { fieldName: { $toInt: "$fieldName" } } } ]); Sample Data db.demo369.insertMany([ { "Price": "1000000" }, ...
Read MoreHow to select a specific subdocument in MongoDB?
To select a specific subdocument in MongoDB, use the find() method with dot notation to query array elements and the $ positional operator in projection to return only the matched subdocument. Syntax db.collection.find( { "arrayField.subfield": "value" }, { "arrayField.$": 1, "_id": 0 } ); Sample Data Let us create a collection with documents containing subdocument arrays ? db.demo37.insertMany([ { "Details": [ ...
Read MoreMongoDB query to retrieve records from a collection named with letters and numbers
When working with MongoDB collections that have names containing letters, numbers, hyphens, and underscores, you must use the db.getCollection() method to access them, as these names cannot be used with standard dot notation. Syntax db.getCollection('collection-name-with-special-chars').find(); db.getCollection('collection-name-with-special-chars').insertOne(document); Create Sample Collection Let's create a collection with a complex name containing letters, numbers, hyphens, and underscores ? db.createCollection('7664734-541d-r5i5f-845575e-ghfhjrjr3747_demo368'); { "ok" : 1 } Insert Sample Data Insert documents into the collection using db.getCollection() ? db.getCollection('7664734-541d-r5i5f-845575e-ghfhjrjr3747_demo368').insertMany([ {"FirstName": "Chris"}, {"FirstName": "David"}, ...
Read MoreIgnore NULL and UNDEFINED values while running a MongoDB query
To ignore NULL and UNDEFINED values while querying in MongoDB, use the $ne (not equal) operator. This operator excludes documents where the specified field is null or undefined. Syntax db.collection.find({"fieldName": {$ne: null}}) Create Sample Data db.demo35.insertMany([ {"Name": "Chris"}, {"Name": null}, {"Name": "Bob"}, {"Name": undefined} ]); { "acknowledged": true, "insertedIds": [ ObjectId("5e175e42cfb11e5c34d898d0"), ...
Read MoreMongoDB query to find on the basis of true or false values
To find documents based on true or false values in MongoDB, use the $exists operator with dot notation to check field presence or use direct boolean value matching. Syntax db.collection.find({"field": { $exists: true/false }}); db.collection.find({"booleanField": true/false}); Sample Data db.demo367.insertMany([ { "Id": "102", "details": [ { "Name": "David" }, { ...
Read MoreMongoDB query to update a MongoDB row with only the objectid
To update a MongoDB document using only its ObjectId, use the update() method with the _id field as the query filter and the $set operator to modify specific fields. Syntax db.collection.update( { "_id": ObjectId("objectid_value") }, { $set: { "field1": "new_value1", "field2": "new_value2" } } ); Sample Data Let us create a collection with sample documents ? db.demo34.insertMany([ { "StudentFirstName": "Chris", "StudentAge": 24 }, { "StudentFirstName": "David", "StudentAge": 23 }, { "StudentFirstName": "Bob", ...
Read MoreMongoDB aggregation framework to sort by length of array?
To sort documents by the length of an array field in MongoDB, use the aggregation framework with $addFields and $size operators to calculate array lengths, then sort by the computed field. Syntax db.collection.aggregate([ { $addFields: { arrayLength: { $size: "$arrayField" } } }, { $sort: { arrayLength: -1 } } ]); Sample Data db.demo33.insertMany([ { "ListOfStudent": ["Chris", "Bob"] }, { "ListOfStudent": ["David", "Adam", "Mike"] }, { "ListOfStudent": ["Carol", "Sam", "John", "Robert"] } ]); ...
Read MoreHow to compare attributes of different objects in MongoDB object array?
To compare attributes of different objects in a MongoDB object array, use $let along with $indexOfArray to locate specific array elements and compare their values using comparison operators. Syntax db.collection.find({ "$expr": { "$let": { "vars": { "element1": {"$arrayElemAt": ["$arrayName", {"$indexOfArray": ["$arrayName.field", "value1"]}]}, ...
Read MoreHow to force MongoDB to use the BasicCursor instead of an index?
To force MongoDB to use a BasicCursor instead of an index, use the hint() method with $natural: 1. This bypasses any existing indexes and performs a collection scan in natural document order. Syntax db.collection.find(query).hint({ $natural: 1 }); Create Sample Data First, let's create an index and insert some test documents ? db.demo31.createIndex({"StudentFirstName": 1}); { "createdCollectionAutomatically": true, "numIndexesBefore": 1, "numIndexesAfter": 2, "ok": 1 } db.demo31.insertMany([ {"StudentFirstName": "John"}, ...
Read MoreMongoDB query to find a specific city record from a collection
To find a specific city record from a MongoDB collection, use the find() method with a query document that matches the desired city name. This allows you to retrieve documents based on specific field values. Syntax db.collection.find({"fieldName": "value"}); Sample Data Let us create a collection with city documents ? db.demo30.insertMany([ {"City": "New York"}, {"City": "Los Angeles"}, {"City": "Chicago"}, {"City": "Los Angeles"} ]); { "acknowledged": true, ...
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