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Articles by Ankith Reddy
Page 26 of 73
Can I retrieve multiple documents from MongoDB by id?
Yes, you can retrieve multiple documents from MongoDB by id using the $in operator. This operator allows you to specify multiple values and returns documents where the field matches any of those values. Syntax db.collection.find({ _id: { $in: [id1, id2, id3, ...] } }); Sample Data Let us create a collection with sample documents ? db.retrieveMultipleDocsByIdDemo.insertMany([ { "_id": 10, "CustomerName": "John" }, { "_id": 14, "CustomerName": "Chris" }, { "_id": 20, "CustomerName": "Robert" }, ...
Read MoreHow to connect to my MongoDB table by command line?
To connect to a MongoDB collection (table) using the command line, you need to first connect to the database and then use the db command with the collection name. Syntax db.collectionName.find(); Step 1: Connect to Database First, switch to your target database and verify the current database ? use sample; db; switched to db sample sample Step 2: List Available Collections Check all collections in the current database ? show collections; arraySizeErrorDemo basicInformationDemo copyThisCollectionToSampleDatabaseDemo deleteAllRecordsDemo deleteDocuments deleteDocumentsDemo deleteSomeInformation documentWithAParticularFieldValueDemo employee findListOfIdsDemo ...
Read MoreHow to remove all documents from a collection except a single document in MongoDB?
To remove all documents from a collection except a single document in MongoDB, use deleteMany() or remove() with the $ne operator to exclude documents that match a specific condition. Syntax db.collection.deleteMany({ field: { $ne: value } }); // OR db.collection.remove({ field: { $ne: value } }); Create Sample Data db.removeAllDocumentsExceptOneDemo.insertMany([ {"StudentName": "Larry", "StudentAge": 21}, {"StudentName": "Mike", "StudentAge": 21, "StudentCountryName": "US"}, {"StudentName": "Chris", "StudentAge": 24, "StudentCountryName": "AUS"} ]); { "acknowledged": true, ...
Read MoreConcatenate strings from two fields into a third field in MongoDB?
To concatenate strings from two fields into a third field in MongoDB, use the $concat operator within an aggregation pipeline with $project stage. Syntax db.collection.aggregate([ { $project: { "newFieldName": { $concat: [ "$field1", "delimiter", "$field2" ] } } } ]); Sample Data db.concatenateStringsDemo.insertMany([ {"StudentFirstName": "John", "StudentLastName": "Doe"}, {"StudentFirstName": "John", "StudentLastName": "Smith"}, {"StudentFirstName": "Carol", "StudentLastName": "Taylor"}, {"StudentFirstName": "David", "StudentLastName": "Miller"}, {"StudentFirstName": "James", "StudentLastName": "Williams"} ]); { ...
Read MoreHow to operate on all databases from the MongoDB shell?
To operate on all databases from MongoDB shell, you can use listDatabases along with adminCommand(). This method retrieves comprehensive information about all databases in your MongoDB instance. Syntax var allDatabaseList = db.adminCommand('listDatabases'); printjson(allDatabaseList); Example First, check the current database with the db command − db; test Now retrieve information about all databases using adminCommand() − var allDatabaseList = db.adminCommand('listDatabases'); printjson(allDatabaseList); { "databases" : [ { ...
Read MoreHow to update MongoDB collection using $toLower?
To update a MongoDB collection using $toLower functionality, use the forEach() method to iterate through documents and apply JavaScript's toLowerCase() function. While $toLower is primarily an aggregation operator, this approach allows you to permanently update field values in your collection. Syntax db.collection.find().forEach( function(document) { document.fieldName = document.fieldName.toLowerCase(); db.collection.save(document); } ); Sample Data First, let's create a collection with mixed-case student names ? db.toLowerDemo.insertMany([ {"StudentId": ...
Read MoreFind oldest/ youngest post in MongoDB collection?
To find oldest/youngest post in MongoDB collection, you can use sort() with limit(1). Use ascending sort (1) for oldest and descending sort (-1) for newest posts based on date fields. Syntax // For oldest post db.collection.find().sort({"dateField": 1}).limit(1); // For newest post db.collection.find().sort({"dateField": -1}).limit(1); Sample Data db.getOldestAndYoungestPostDemo.insertMany([ { "UserId": "Larry@123", "UserName": "Larry", "UserPostDate": new ISODate('2019-03-27 12:00:00') }, ...
Read MoreHow to return only a single property "_id" in MongoDB?
To return only the _id property in MongoDB, use the projection parameter in the find() method by setting {"_id": 1}. This filters the output to show only the _id field from all matching documents. Syntax db.collectionName.find({}, {"_id": 1}); Sample Data Let us create a collection with sample documents : db.singlePropertyIdDemo.insertMany([ {"_id": 101, "UserName": "Larry", "UserAge": 21}, {"_id": 102, "UserName": "Mike", "UserAge": 26}, {"_id": 103, "UserName": "Chris", "UserAge": 24}, {"_id": 104, "UserName": "Robert", "UserAge": 23}, ...
Read MoreUpsert in MongoDB while using custom _id values to insert a document if it does not exist?
To perform an upsert with custom _id values in MongoDB, use update() with the upsert option instead of insert(). When you use insert() with existing _id values, MongoDB throws a duplicate key error. The upsert operation inserts a document if it doesn't exist or updates it if it does. Syntax db.collection.update( { "_id": customIdValue }, { $set: { field1: "value1", field2: "value2" } }, { upsert: true } ); Sample Data First, let's create a collection and demonstrate the duplicate key error ...
Read MoreFind all the non-distinct values of a field in MongoDB?
To find all non-distinct values of a field in MongoDB, use the aggregate() method with $group to count occurrences and $match to filter values that appear more than once. Syntax db.collection.aggregate([ { $group: { "_id": "$fieldName", "count": { $sum: 1 } }}, { $match: { "count": { $gt: 1 } }} ]); Sample Data ...
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