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MongoDB Articles
Page 5 of 111
MongoDB query to add a new field and concatenate the price result divided by a specific number in it
To add a new field and concatenate price results divided by a specific number in MongoDB, use the $addFields stage with $reduce and $map operators to process array values and combine them into a single string. Syntax db.collection.aggregate([ { $addFields: { newField: { $reduce: { ...
Read MoreHow can I sort documents in MongoDB 4 and display only a single field?
To sort documents in MongoDB and display only a single field, use the sort() method combined with projection. The sort() method orders documents, while projection controls which fields appear in the result. Syntax db.collection.find({}, {fieldName: 1}).sort({fieldName: 1}); Where 1 means ascending order and -1 means descending order. Sample Data db.demo611.insertMany([ {"Name": "Chris"}, {"Name": "Adam"}, {"Name": "John"}, {"Name": "Bob"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreHow to add together a subset of elements of an array in MongoDB aggregation?
To add together a subset of elements of an array in MongoDB aggregation, use the $slice operator combined with $sum to select and sum specific array elements based on position or range. Syntax db.collection.aggregate([ { $project: { subsetSum: { $sum: { ...
Read MoreMongoDB query to remove entire array from collection?
To remove an entire array field from all documents in a MongoDB collection, use the $unset operator. This completely removes the specified field from the documents. Syntax db.collection.updateMany( {}, { $unset: { "arrayFieldName": "" } } ); Sample Data Let us create a collection with documents containing array fields ? db.demo609.insertMany([ { "ListOfSubject": ["MySQL", "MongoDB"] }, { "ListOfSubject": ["Java"] } ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreGetting unique values within two arrays in one MongoDB document
To get unique values within two arrays in a MongoDB document, use the $setUnion operator in the aggregation pipeline. The $setUnion takes two or more arrays and returns an array containing the unique elements that appear in any input array. Syntax db.collection.aggregate([ { $project: { uniqueArray: { $setUnion: ["$array1", "$array2"] } } } ]) Sample Data Let us ...
Read MoreMongoDB query to update the nested document?
To update a nested document in MongoDB, use the update() method with dot notation to specify the path to the nested field. This allows you to modify deeply embedded values without affecting the parent document structure. Syntax db.collection.update( { "filterField": "value" }, { $set: { "parentField.nestedField.targetField": "newValue" } } ); Sample Data Let us create a collection with a nested document structure ? db.demo607.insertOne({ id: 1, "Info1": { ...
Read MoreHow to get a rating average in MongoDB based on duplicate ids?
To get a rating average in MongoDB based on duplicate ids, use the $avg operator with $group. The $ifNull operator handles null rating values by treating them as zero in the calculation. Syntax db.collection.aggregate([ { "$group": { "_id": "$fieldToGroupBy", "averageField": { "$avg": { "$ifNull": ["$ratingField", 0] } } } ...
Read MoreUpdate quantity in MongoDB based on two conditions?
To update quantity in MongoDB based on two conditions, use the update() method with multiple filter criteria. Combine document-level and array element conditions to target specific nested objects. Syntax db.collection.update( { "documentField": "value", "arrayField.nestedField": "arrayValue" }, { $set: { "arrayField.$.targetField": newValue } } ); Sample Data db.demo605.insertMany([ { _id: 1, ...
Read MoreHow to remove duplicates from MongoDB Collection?
To remove duplicates from a MongoDB collection, create a unique index on the field that should not have duplicate values. This prevents duplicate insertion and removes existing duplicates when combined with the dropDups option. Syntax db.collectionName.createIndex( { fieldName: 1 }, { unique: true, dropDups: true } ); Example: Preventing Duplicate FirstNames Let's create a unique index on the FirstName field to prevent duplicates ? db.demo604.createIndex( { FirstName: 1 }, { unique: true, dropDups: true ...
Read MoreDifference between NumberLong(x) and NumberLong("x") in MongoDB?
The NumberLong(x) function can lose precision with very large integers due to JavaScript's number limitations, while NumberLong("x") preserves exact precision by accepting the number as a string. Syntax NumberLong(number) // May lose precision for very large values NumberLong("string") // Preserves exact precision Example Let us create a collection with documents to demonstrate the difference ? db.demo603.insertMany([ {"longValue": NumberLong(988998985857575789)}, {"longValueInString": NumberLong("988998985857575789")} ]); { "acknowledged": true, "insertedIds": ...
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