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Big Data Analytics Articles
Page 30 of 135
Working with MongoDB find()
The find() method in MongoDB selects documents in a collection or view and returns a cursor to the selected documents. It is the primary method for querying data from MongoDB collections. Syntax db.collection.find(query, projection) Parameters: query (optional): Specifies selection criteria using query operators projection (optional): Specifies which fields to return Sample Data Let us create a collection with sample documents ? db.demo405.insertMany([ {"StudentInfo": {"Name": "Chris"}}, {"StudentInfo": {"Name": "David"}}, {"StudentInfo": {"Name": "Bob"}}, {"StudentInfo": {"Name": ...
Read MoreTransaction lock in MongoDB?
In MongoDB versions prior to 4.0, native transactions weren't available. To implement transaction-like locking behavior, you can use findOneAndUpdate() with a lock field to ensure atomic operations on documents. Syntax db.collection.findOneAndUpdate( { "lock_field": { "$exists": false } }, { "$set": { "lock_field": true } } ) Sample Data db.demo404.insertMany([ { "FirstName": "John" }, { "FirstName": "Robert" }, { "FirstName": "Mike" } ]); { "acknowledged": true, ...
Read MoreMongoDB query to sort by words
To sort by words in a custom order in MongoDB, use $addFields with $cond to assign priority values to specific words, then sort by those values. Syntax db.collection.aggregate([ { $addFields: { sortByWords: { $cond: [ { $eq: ...
Read MoreHow we can perform sort on ObjectId column in MongoDB?
To perform sort on ObjectId column in MongoDB, use the sort() method with the _id field. ObjectIds are sorted by their creation timestamp, making them useful for chronological ordering. Syntax db.collection.find().sort({_id: 1}); // Ascending (oldest first) db.collection.find().sort({_id: -1}); // Descending (newest first) Sample Data db.demo403.insertMany([ {"Name": "Chris"}, {"Name": "David"}, {"Name": "Bob"}, {"Name": "Adam"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreHow to get the intersection of two arrays in MongoDB?
To get intersection of two arrays in MongoDB, use $setIntersection along with aggregate(). This operator returns an array containing elements that appear in both input arrays. Syntax db.collection.aggregate([ { $project: { fieldName: { $setIntersection: ["$array1", "$array2"] } } } ]); Sample Data Let us create a collection with documents ? db.demo61.insertOne({ "Values1": ...
Read MoreMongoDB query to get date records in a range
To get date records in a range, use the $gt (greater than) and $lt (less than) operators together to define the date boundaries for your query. Syntax db.collection.find({ "dateField": { "$gt": ISODate("start-date"), "$lt": ISODate("end-date") } }); Sample Data db.demo60.insertMany([ {"ArrivalDate": new ISODate("2019-01-11 12:30:10")}, {"ArrivalDate": new ISODate("2019-10-12 03:10:00")}, {"ArrivalDate": new ISODate("2019-01-14 05:11:20")} ]); { ...
Read MoreSet multiple conditions in MongoDB and fetch value in a range
To set multiple conditions in MongoDB and fetch values in a range, use comparison operators like $gt (greater than) and $lt (less than) combined in a single query. This allows you to filter documents based on numeric ranges or multiple criteria. Syntax db.collection.find({ field: { $gt: minValue, $lt: maxValue } }); Sample Data db.demo59.insertMany([ { "Values": 50 }, { "Values": 10 }, { "Values": 58 }, { "Values": 78 } ]); ...
Read MoreHow to update a MongoDB document without overwriting the existing one?
To update only a field value in MongoDB, use update() along with $set. This won't overwrite the existing document but only modifies the specified fields. Syntax db.collection.update( { "field": "matchValue" }, { $set: { "fieldToUpdate": "newValue" } } ); Sample Data Let us first create a collection with documents ? db.demo401.insertOne({ "_id": 1001, "Name": "Chris", "SubjectName": "MongoDB", "Score": 45 }); { "acknowledged": true, "insertedId": 1001 ...
Read MoreMongoDB query to update only a single item from voting (up and down) records?
To update a single field in MongoDB voting records, use the $inc operator to increment or decrement vote counts. This allows you to modify only the TotalVote field without affecting other document properties. Syntax db.collection.update( { "field": "matchValue" }, { $inc: { "fieldToUpdate": incrementValue } } ); Create Sample Data Let us first create a collection with voting records − db.demo57.insertMany([ { "Votes": { "VoterName": "Chris", "TotalVote": 50 } }, { "Votes": { "VoterName": "David", "TotalVote": ...
Read MoreHow to copy attributes in MongoDB?
To copy the value of one attribute to another in MongoDB, use $set with forEach() to iterate through documents and update each one by copying the source field value to the target field. Syntax db.collection.find({}).forEach(function(doc) { db.collection.update( { _id: doc._id }, { $set: { targetField: doc.sourceField } } ); }); Sample Data db.demo55.insertMany([ { "ShippingDate": "", "date": new ISODate("2019-01-21") }, ...
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