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Articles on Trending Technologies
Technical articles with clear explanations and examples
MongoDB query to find records with keys containing dots?
To find MongoDB records containing field names with dots, use the aggregation pipeline with $addFields, $objectToArray, and $filter operators. The $indexOfBytes operator detects dot characters in field names. Syntax db.collection.aggregate([ { $addFields: { result: { $filter: { ...
Read MoreFetch multiple documents in MongoDB query with OR condition?
To fetch multiple documents in MongoDB using OR condition, use the $or operator which performs a logical OR operation on an array of expressions and selects documents that satisfy at least one of the expressions. Syntax db.collection.find({ $or: [ { field1: value1 }, { field2: value2 }, { field3: value3 } ] }); Sample Data db.demo362.insertMany([ { ...
Read MoreUsing object as key for finding values in MongoDB
To use an object field as a key for finding values in MongoDB, use dot notation to access nested object properties in the projection parameter of the find() method. Syntax db.collection.find({}, {"objectName.fieldName": 1}); Sample Data Let us create a collection with nested object documents − db.demo361.insertMany([ {"details": {"FirstName": "Chris", "LastName": "Brown"}}, {"details": {"FirstName": "David", "LastName": "Miller"}}, {"details": {"FirstName": "John", "LastName": "Doe"}} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreFind current and previous documents in MongoDB
To get the current and previous documents in MongoDB, use sort() with limit() to retrieve the most recent documents based on a specific criteria. This approach helps you find the latest two records that match your query conditions. Syntax db.collection.find( { field: { $lte: value } }, { projection } ).sort({ _id: -1 }).limit(2); Sample Data Let us create a collection with sample documents: db.demo360.insertMany([ { id: 101, "Name": "Chris" }, { id: 102, "Name": "David" ...
Read MoreMongoDB query to concatenate values of array with other fields
To concatenate values of an array with other fields in MongoDB, use $reduce to convert the array into a single string, then $concat to combine it with other fields in the $project stage. Syntax db.collection.aggregate([ { $project: { arrayAsString: { $reduce: { ...
Read MoreDoes aggregation query with $match works in MongoDB?
Yes, the $match operator works perfectly in MongoDB aggregation queries. It filters documents in the aggregation pipeline, similar to the find() method's query criteria, but as the first stage of data processing. Syntax db.collection.aggregate([ { $match: { "field": "value" } }, // Additional pipeline stages... ]); Sample Data db.demo358.insertMany([ { "ClientId": 101, "ClientName": "Chris", "ClientAge": 34 }, { "ClientId": 102, "ClientName": "David", "ClientAge": 32 }, { "ClientId": 103, "ClientName": "David", "ClientAge": 35 }, ...
Read MoreMongoDB query to fetch a specific document rom documents with field value set using NumberInt()?
To fetch a specific document from MongoDB where a field value is set using NumberInt(), use dot notation to target nested fields and match the exact NumberInt() value in your query. Syntax db.collection.find({"field.nestedField": NumberInt(value)}); Sample Data Let us create a collection with documents containing NumberInt() values − db.demo357.insertMany([ { "FirstName": "Chris", "Age": 21, "details": { ...
Read MoreHow to validate documents before insert or update in MongoDB?
MongoDB provides built-in document validation to enforce data quality rules before inserting or updating documents. Use the validator option during collection creation to define validation criteria using MongoDB query operators. Syntax db.createCollection("collectionName", { validator: { $jsonSchema: { /* validation rules */ } // OR /* MongoDB query expression */ }, validationLevel: "strict", // or "moderate" validationAction: "error" ...
Read MoreHow to project specific elements in an array field with MongoDB?
To project specific elements in an array field in MongoDB, use the $project stage with $filter to conditionally include array elements that match your criteria. Syntax db.collection.aggregate([ { $project: { arrayField: { $filter: { input: "$arrayField", ...
Read MoreMongoDB query for counting number of unique fields grouped by another field?
To count the number of unique field combinations grouped by another field in MongoDB, use the aggregation pipeline with $group stages. First group by the unique combinations, then group again by the target field to count occurrences. Syntax db.collection.aggregate([ { $group: { _id: { "groupField": "$groupField", ...
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