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Database Articles
Page 27 of 547
MongoDB query to add timestamp only if it is not present
To add a timestamp field only if it is not already present in MongoDB documents, use the $exists operator with update() and set multi: true to update multiple documents at once. Syntax db.collection.update( { "fieldName": { $exists: false } }, { $set: { "fieldName": new Date() } }, { multi: true } ); Sample Data db.demo479.insertMany([ { "DueDate": ISODate("2020-01-10"), "Name": "Chris" }, { "Name": "David" }, { "DueDate": ISODate("2019-12-31"), ...
Read MoreMongoDB $unwind to get the count
The $unwind operator in MongoDB deconstructs an array field from input documents to output a separate document for each array element. Use $unwind with $group and $count in an aggregation pipeline to get counts of array elements. Syntax db.collection.aggregate([ { $unwind: "$arrayField" }, { $group: { _id: "$groupField", count: { $sum: 1 } } } ]); Sample Data db.demo478.insertMany([ { "Details": { ...
Read MoreGet the real document BSON size in MongoDB?
You can use Object.bsonsize() to get the real document BSON size in MongoDB. This method prints the BSON size of a document in bytes, which is useful for understanding storage requirements and optimizing document structure. Syntax Object.bsonsize(document) Sample Data Let us create a collection with documents ? db.demo477.insertMany([ {"ClientId": 1, "ClientName": "Chris"}, {"ClientId": 2, "ClientName": "David"}, {"ClientId": 3, "ClientName": "Bob"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreMongoDB query to update all documents matching specific IDs
To update all documents matching specific IDs in MongoDB, use updateMany() with the $in operator to specify multiple ID values in the filter criteria. Syntax db.collection.updateMany( { _id: { $in: [id1, id2, id3] } }, { $set: { field: "newValue" } } ); Sample Data db.demo476.insertMany([ { _id: 1, "Name": "Chris" }, { _id: 2, "Name": "David" }, { _id: 3, "Name": "Bob" }, { _id: 4, "Name": "Carol" ...
Read MoreMongoDB query to check the existence of multiple fields
To check the existence of multiple fields in MongoDB, use the $exists operator combined with $and. This query returns documents that contain all specified fields. Syntax db.collection.find({ $and: [ { "field1": { $exists: true } }, { "field2": { $exists: true } }, { "field3": { $exists: true } } ] }); Sample Data db.demo475.insertMany([ { "StudentFirstName": ...
Read MoreMongoDB function to return a specific data/value?
To return a specific data/value in MongoDB, use the findOne() method. The findOne() method returns the first document that satisfies the specified query criteria from the collection. Syntax db.collection.findOne(query, projection) Create Sample Data Let us create a collection with documents ? db.demo473.insertMany([ { "_id": ObjectId(), "Name": "Chris", "details": { "X-Coordinate": 10, ...
Read MoreFinding documents in MongoDB collection where a field is equal to given integer value?
To find documents where a field is equal to a given integer value, use the find() method with the field name and integer value in the query condition. Syntax db.collection.find({"fieldName": integerValue}); Sample Data Let us create a collection with documents − db.demo472.insertMany([ {"Project_Id": -101, "ProjectName": "Online Customer Tracking"}, {"Project_Id": 101, "ProjectName": "Online Banking System"}, {"Project_Id": 102, "ProjectName": "Online Library System"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreHow to remove primary key from MongoDB?
To remove the primary key (_id field) from query results in MongoDB, use projection with the _id: 0 option in the find() method. This excludes the _id field from the returned documents without deleting it from the database. Syntax db.collection.find({}, {_id: 0}); db.collection.find({}, {_id: 0, field1: 1, field2: 1}); Sample Data db.demo471.insertMany([ {"ClientId": 101, "ClientName": "Chris"}, {"ClientId": 102, "ClientName": "Bob"}, {"ClientId": 103, "ClientName": "David"} ]); { "acknowledged": true, "insertedIds": [ ...
Read MoreReturn all ages records that are ints with a MongoDB query
To return all age records that are integers from a collection containing both string and integer age values, use the $type operator. The $type operator in MongoDB selects documents where the field value matches the specified BSON data type. Syntax db.collection.find({ "fieldName": { $type: "number" } }); Create Sample Data Let us create a collection with documents containing both integer and string age values ? db.demo470.insertMany([ { "Age": 23 }, { "Age": "Unknown" }, { "Age": 24 }, ...
Read MoreHow do you find a MongoDB record that is two level deep?
To find a MongoDB record that is two level deep, use the $where operator with a JavaScript function to loop through nested objects and find matching field values. Syntax db.collection.find({ $where: function() { for (var field in this) { if (this[field]["nestedField"] == "searchValue") { return true; ...
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