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Articles by Chandu yadav
Page 27 of 81
Building Multiple Indexes at once in MongoDB?
To build multiple indexes at once in MongoDB, use the createIndexes() method and pass multiple index specifications in an array. This approach is more efficient than creating indexes one by one. Syntax db.collection.createIndexes([ { "field1": 1 }, { "field2": -1 }, { "field3": 1, "field4": 1 } ]); Example Let's create multiple single-field indexes on a collection ? db.multipleIndexesDemo.createIndexes([ {"First": 1}, {"Second": 1}, {"Third": 1}, ...
Read MoreHow do you limit an array sub-element in MongoDB?
You can use $slice operator to limit array elements in MongoDB query results. The $slice operator controls how many elements from an array field are returned in the projection. Syntax db.collection.find( {}, { "arrayField": { $slice: N } } ) Where N can be: Positive number: Returns first N elements Negative number: Returns last N elements [skip, limit]: Skips elements and limits result Sample Data db.limitAnArrayDemo.insertOne({ _id: 101, "PlayerName": "Bob", ...
Read MoreGet component of Date / ISODate in MongoDB?
To get component of Date/ISODate in MongoDB, you can access individual date components like year, month, day, hour, minute, and second using JavaScript date methods on the ISODate field. Syntax // Access date field var dateField = db.collection.findOne().dateFieldName; // Get components dateField.getFullYear() // Year (e.g., 2019) dateField.getMonth() // Month (0-11, January=0) dateField.getDate() // Day of month (1-31) dateField.getHours() // Hour (0-23) dateField.getMinutes() // Minutes (0-59) dateField.getSeconds() ...
Read MoreCheck if MongoDB database exists?
To check if a MongoDB database exists, use the indexOf() method on the list of database names. This returns the index position if the database exists, or -1 if it doesn't exist. Syntax db.getMongo().getDBNames().indexOf("databaseName"); Return Values Positive number (0 or greater): Database exists at that index position -1: Database does not exist Case 1: Database Exists Check if the "test" database exists ? db.getMongo().getDBNames().indexOf("test"); 6 The result 6 means the "test" database exists and is located at index 6 in the database list. ...
Read MoreGet MongoDB Databases in a JavaScript Array?
To get MongoDB databases in a JavaScript array, you can use the listDatabases command with runCommand() and then extract database names into an array using JavaScript. Syntax use admin; allDatabasesDetails = db.runCommand({listDatabases: 1}); databaseNames = allDatabasesDetails.databases.map(db => db.name); Step 1: Get All Databases Details First, switch to the admin database and run the listDatabases command ? use admin; allDatabasesDetails = db.runCommand({listDatabases: 1}); { "databases" : [ { "name" : "admin", ...
Read MoreMongoDB equivalent of SELECT field AS `anothername`?
In MySQL, we give an alias name for a column. Similarly, you can give an alias name for field name in MongoDB using the $project stage in aggregation pipeline. Syntax db.collectionName.aggregate([ { "$project": { "_id": 0, "aliasName": "$originalFieldName" }} ]); Sample Data Let us first create a collection with documents ? db.selectFieldAsAnotherNameDemo.insertMany([ {"Name": "Larry"}, {"Name": "Robert"}, ...
Read MoreMongoDB 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, ...
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