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Articles on Trending Technologies
Technical articles with clear explanations and examples
Get distinct levels of array field in MongoDB?
To get distinct levels of array field in MongoDB, use the $addToSet operator within an aggregation pipeline. This operator collects unique values and prevents duplicates when grouping array fields. Syntax db.collection.aggregate([ { $group: { "_id": null, "fieldName": { $addToSet: "$arrayField" } } } ]); Sample Data ...
Read MoreMongoDB query to implement aggregate function
MongoDB aggregate functions allow you to perform data processing operations on collections, such as filtering, grouping, and transforming documents. The aggregation pipeline processes documents through multiple stages to produce computed results. Syntax db.collection.aggregate([ { $match: { field: value } }, { $unwind: "$arrayField" }, { $group: { _id: "$field", operation: { $operator: expression } } } ]) Sample Data Let us first create a collection with documents ? db.demo121.insertOne({ "Id": 101, "Details": ...
Read MoreMongoDB query for ranking / search count?
To implement ranking or search count in MongoDB, use the aggregation pipeline with $setIntersection to find matching elements and $divide to calculate a relevance score based on the ratio of matched terms to total document elements. Syntax db.collection.aggregate([ { "$match": { "fieldName": { "$in": searchArray } } }, { "$addFields": { "rankScore": { "$divide": [ ...
Read MoreSelect special fields rather than all in MongoDB
To select specific fields instead of all fields in MongoDB, use field projection in the find() method. Set unwanted fields to 0 to exclude them, or set wanted fields to 1 to include only those fields. Syntax db.collection.find({}, {field1: 0, field2: 0}); // Exclude fields db.collection.find({}, {field1: 1, field2: 1}); // Include only these fields Sample Data db.demo269.insertMany([ {StudentId: 101, StudentSubject: "MySQL"}, {StudentId: 102, StudentSubject: "Java"}, {StudentId: 103, StudentSubject: "MongoDB"}, {StudentId: 104, StudentSubject: "C"} ]); ...
Read MoreUse MongoDB Aggregate and select only top record (descending)
To select only the top record in descending order using MongoDB aggregate, use the $sort stage to order documents and the $limit stage to restrict the result to one document. Syntax db.collection.aggregate([ { $sort: { fieldName: -1 } }, { $limit: 1 } ]); Sample Data db.demo267.insertMany([ { id: 100, "Name": "Chris" }, { id: 100, "Name": "Adam" }, { id: 100, "Name": "David" }, { id: 100, "Name": ...
Read MoreHow to query with nand operator in MongoDB?
MongoDB doesn't have a $nand operator, but you can achieve NAND (Not AND) logic by using $or with $ne operators. This returns documents where at least one condition is false. Syntax db.collection.find({ $or: [ { "field1": { $ne: value1 } }, { "field2": { $ne: value2 } } ] }); Sample Data db.demo266.insertMany([ { "active1": true, "active2": false }, { "active1": ...
Read MoreMongoDB query to update only certain fields?
To update only certain fields in MongoDB, use the $set operator. This operator modifies specific fields without affecting other existing fields in the document. Syntax db.collection.update( { "field": "value" }, { $set: { "fieldToUpdate": "newValue" } } ); Sample Data Let us create a collection with sample documents − db.demo265.insertMany([ {"id": 101, "Name": "Chris"}, {"id": 102, "Name": "Bob"}, {"id": 103, "Name": "David"} ]); { "acknowledged": ...
Read MoreUsing count equivalent in MongoDB to find top users with max occurrence
To find the top users with maximum occurrence in MongoDB, use the $group stage with aggregate() to count occurrences, then $sort and $limit to get the top results. Syntax db.collection.aggregate([ { $group: { _id: "$fieldName", count: { $sum: 1 } } }, { $sort: { count: -1 } }, { $limit: numberOfTopResults } ]); Sample Data Let us create a collection with user documents ? db.demo264.insertMany([ { "Name": "Chris" }, { "Name": ...
Read MoreMongoDB query to skip documents
To skip documents in MongoDB, use the skip() method. This method allows you to skip a specified number of documents from the beginning of the result set, useful for pagination and result navigation. Syntax db.collection.find().skip(number) Sample Data db.demo263.insertMany([ {_id: 100}, {_id: 200}, {_id: 300} ]); { "acknowledged": true, "insertedIds": { "0": 100, "1": 200, "2": 300 } } ...
Read MoreInvert Result of MongoDB Query (Implement Opposite of $and operation)?
To invert the result of a MongoDB query (opposite of $and operation), use $or combined with $ne operators. This applies De Morgan's Law: NOT (A AND B) = (NOT A) OR (NOT B). Syntax db.collection.find({ $or: [ { "field1": { $ne: "value1" } }, { "field2": { $ne: "value2" } } ] }); Sample Data db.demo4.insertMany([ { uid: 1, "Name": "Chris", "Age": 22 }, ...
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