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Articles by Nishtha Thakur
Page 14 of 40
How do I display the indexes of a collection in MongoDB?
To display the indexes of a collection in MongoDB, use the getIndexes() method. This method returns information about all indexes defined on the specified collection, including the default _id index. Syntax db.collectionName.getIndexes(); Sample Data Let's create a collection with sample documents ? db.indexDemo.insertMany([ { "StudentName": "Larry", "StudentAge": 21 }, { "StudentName": "Mike", "StudentAge": 24 }, { "StudentName": "Carol", "StudentAge": 20 } ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreMongoDB query with an 'or' condition?
The $or operator in MongoDB performs a logical OR operation on an array of expressions and returns documents that match at least one of the conditions. It's useful when you need to query documents based on multiple alternative criteria. Syntax db.collection.find({ $or: [ { field1: value1 }, { field2: value2 }, { field3: { $operator: value3 } } ] }); Sample Data ...
Read MoreResolve 'multi update only works with $ operators' in MongoDb?
The "multi update only works with $ operators" error occurs when trying to update multiple documents without using MongoDB's update operators like $set. To resolve this, use update operators when the multi flag is set to true. Syntax db.collection.update( { /* query */ }, { $set: { "fieldName": "newValue" } }, { multi: true } ) Sample Data db.unconditionalUpdatesDemo.insertMany([ { "ClientName": "Larry", "ClientAge": 24 }, { "ClientName": "Mike", "ClientAge": 26 }, ...
Read MoreClone a collection in MongoDB?
To clone a collection in MongoDB, use the forEach() method to iterate through documents and insert them into a new collection. This creates an exact copy with all documents and their _id values preserved. Syntax db.sourceCollection.find().forEach(function(doc) { db.targetCollection.insert(doc); }); Sample Data First, let's create a collection with sample documents ? db.studentInformation.insertMany([ {"StudentName": "Chris"}, {"StudentName": "Robert"}, {"StudentName": "James"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreMongoDB Query to select records having a given key?
To select records having a given key, you can use the $exists operator. This operator checks whether a field exists in the document, regardless of its value. Syntax db.collectionName.find({ fieldName: { $exists: true } }); Sample Data Let's create a collection with sample documents to demonstrate the $exists operator ? db.selectRecordsHavingKeyDemo.insertMany([ {"StudentName": "John", "StudentAge": 21, "StudentMathMarks": 78}, {"StudentName": "Carol", "StudentMathMarks": 89}, {"StudentName": "Sam", "StudentAge": 26, "StudentMathMarks": 89}, {"StudentName": "Sam", "StudentMathMarks": 98} ]); { ...
Read MoreHow to remove object from array in MongoDB?
You can use $pull operator to remove objects from an array in MongoDB. The $pull operator removes all array elements that match a specified query condition. Syntax db.collection.update( { "matchField": "value" }, { $pull: { "arrayField": { "field": "value" } } } ); Sample Data Let us create a collection with a document containing an array of objects ? db.removeObjectFromArrayDemo.insertOne({ "StudentName": "John", "StudentAcademicProjectDetails": [ { ...
Read MoreMongoDB query condition on comparing 2 fields?
To query documents by comparing two fields in MongoDB, you can use the $where operator with JavaScript expressions or the more efficient $expr operator with aggregation expressions. Syntax // Using $where (JavaScript) db.collection.find({ $where: function() { return this.field1 < this.field2; } }); // Using $expr (Recommended) db.collection.find({ $expr: { $lt: ["$field1", "$field2"] } }); Sample Data db.comparingTwoFieldsDemo.insertMany([ { ...
Read MoreFind items that do not have a certain field in MongoDB?
To find documents that do not have a certain field in MongoDB, use the $exists operator with the value false. This operator checks whether a field is present in the document, regardless of its value. Syntax db.collection.find({"fieldName": {$exists: false}}) Sample Data Let's create a collection with documents where some have a specific field and others don't ? db.findDocumentDoNotHaveCertainFields.insertMany([ {"UserId": 101, "UserName": "John", "UserAge": 21}, {"UserName": "David", "UserAge": 22, "UserFavouriteSubject": ["C", "Java"]}, {"UserName": "Bob", "UserAge": 24, "UserFavouriteSubject": ["MongoDB", "MySQL"]} ]); ...
Read MoreHow to stop MongoDB in a single command?
To stop MongoDB in a single command, use the shutdown command with the --eval option to execute the shutdown operation directly from the command line without entering the MongoDB shell. Syntax mongo --eval "db.getSiblingDB('admin').shutdownServer()" Example: Stopping MongoDB Server Execute the shutdown command from your system's command prompt or terminal ? mongo --eval "db.getSiblingDB('admin').shutdownServer()" The output shows the MongoDB server shutting down ? MongoDB shell version v4.0.5 connecting to: mongodb://127.0.0.1:27017/?gssapiServiceName=mongodb Implicit session: session { "id" : UUID("c0337c02-7ee2-45d9-9349-b22d6b1ffe85") } MongoDB server version: 4.0.5 server should be down... 2019-03-14T21:56:10.327+0530 I NETWORK ...
Read MorePrettyprint in MongoDB shell as default?
You can call pretty() function on cursor object to format MongoDB query output in a readable, indented JSON format. This is especially useful for documents with nested arrays and objects. Syntax db.collectionName.find().pretty(); Sample Data Let us create a collection with sample documents ? db.prettyDemo.insertMany([ { "ClientName": "Larry", "ClientAge": 27, "ClientFavoriteCountry": ["US", "UK"] }, { ...
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