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Articles by Chandu yadav
Page 30 of 81
MongoDB query which represents not equal to null or empty?
To set a query for not equal to null or empty, use the $nin operator. This operator selects documents where the field value is not in the specified array of values, effectively filtering out null and empty string values. Syntax db.yourCollectionName.find({yourFieldName: {$nin: [null, ""]}}); Sample Data db.notEqualToNullOrEmptyDemo.insertMany([ {"UserName": "Larry", "UserAge": 24}, {"UserName": "", "UserAge": 29}, {"UserName": "Sam", "UserAge": 32}, {"UserName": null, "UserAge": 27}, {"UserName": "Robert", "UserAge": 26}, {"UserName": "", ...
Read MoreHow to delete multiple ids in MongoDB?
To delete multiple documents by their IDs in MongoDB, use the $in operator with the remove() or deleteMany() method. This allows you to specify multiple ObjectIds in a single query. Syntax db.collectionName.remove({ _id: { $in: [ObjectId("id1"), ObjectId("id2"), ObjectId("id3")] } }); Or using the modern deleteMany() method: db.collectionName.deleteMany({ _id: { $in: [ObjectId("id1"), ObjectId("id2"), ObjectId("id3")] } }); Sample Data db.deleteMultipleIdsDemo.insertMany([ {"ClientName": "Chris", "ClientAge": 26}, {"ClientName": "Robert", "ClientAge": 28}, ...
Read MoreHow to find exact Array Match with values in different order using MongoDB?
To find exact array match with values in different order in MongoDB, use the $all operator combined with $size. The $all operator matches arrays containing all specified elements regardless of order, while $size ensures the exact array length. Syntax db.collection.find({ "arrayField": { "$size": exactLength, "$all": [value1, value2, value3] } }); Create Sample Data db.exactMatchArrayDemo.insertMany([ { "StudentName": "David", ...
Read MoreCan I query on a MongoDB index if my query contains the $or operator?
Yes, you can query on MongoDB indexes with the $or operator. MongoDB can effectively use separate indexes for each condition in the $or query, combining results through an OR stage in the execution plan. Syntax db.collection.find({ $or: [ { field1: value1 }, { field2: value2 } ]}).explain(); Create Sample Indexes First, create indexes on the fields you'll query ? db.indexOrQueryDemo.createIndex({"First": 1}); { "createdCollectionAutomatically": false, "numIndexesBefore": 2, "numIndexesAfter": 3, ...
Read MoreGet the first element in an array and return using MongoDB Aggregate?
To get the first element from an array using MongoDB aggregation, use the $arrayElemAt operator or combine $unwind with $first. The $arrayElemAt method is simpler and more efficient for this task. Syntax db.collection.aggregate([ { $project: { "fieldName": { $arrayElemAt: ["$arrayField", 0] } } } ]); Sample Data db.getFirstElementInArrayDemo.insertMany([ { ...
Read MoreHow to reduce MongoDB storage space after deleting large amount of data?
To reduce MongoDB storage space after deleting a large amount of data, you need to reclaim the freed disk space since MongoDB doesn't automatically release space after deletions. The database continues to use the same amount of disk space even after documents are removed. Syntax db.runCommand({ "compact": "collectionName" }) Or for the entire database: db.repairDatabase() Method 1: Using compact Command (Recommended) The compact command is the modern approach to reclaim space from a specific collection ? db.runCommand({ "compact": "users" }) { "ok" : 1, "bytesFreed" ...
Read MoreIs it possible to sum two fields in MongoDB using the Aggregation framework?
Yes, it is possible to sum two fields in MongoDB using the $add operator within the $project stage of the aggregation framework. This creates a new computed field containing the sum of existing fields. Syntax db.collection.aggregate([ { $project: { field1: "$field1", field2: "$field2", sumField: { $add: ["$field1", "$field2"] } ...
Read MorePerform conditional upserts or updates in MongoDB
In MongoDB, you can perform conditional updates that only modify a field if certain conditions are met. The $max operator is particularly useful for conditional updates - it only updates a field if the new value is greater than the current value. Syntax db.collection.update( { "field": "matchValue" }, { $max: { "fieldToUpdate": newValue } } ); Sample Data Let us create a collection with sample student score documents ? db.conditionalUpdatesDemo.insertMany([ { "_id": ...
Read MoreOnly insert if a value is unique in MongoDB else update
To only insert if a value is unique in MongoDB (or update if it exists), use the upsert option with the update() method. When upsert: true is specified, MongoDB performs an update if the document matches the query criteria, or inserts a new document if no match is found. Syntax db.collection.update( { field: "matchValue" }, { $set: { field: "newValue" } }, { upsert: true } ); Sample Data db.onlyInsertIfValueIsUniqueDemo.insertMany([ {"StudentName": "Larry", "StudentAge": 22}, ...
Read MoreQuery MongoDB with length criteria?
To query MongoDB with length criteria, you can use the $regex operator with regular expressions to match string fields based on their character length. Syntax db.collection.find({ "fieldName": { $regex: /^.{minLength, maxLength}$/ } }); Where minLength and maxLength define the character count range. Sample Data db.queryLengthDemo.insertMany([ {"StudentFullName": "John Smith"}, {"StudentFullName": "John Doe"}, {"StudentFullName": "David Miller"}, {"StudentFullName": "Robert Taylor"}, {"StudentFullName": "Chris Williams"} ]); { ...
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