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MongoDB Articles
Page 80 of 111
Is there a way to limit the number of records in a certain MongoDB collection?
Yes, you can use capped parameter along with max size. Following is the syntax −db.createCollection("yourCollectionName", {capped:true, size:yourSizeInBytes, max:howManyRecordsYouWant})Let us first create a collection with capped:true −> db.createCollection("limitTheNumberOfRecordsDemo", {capped:true, size:200024, max:3}) { "ok" : 1 }We will now create a collection with documents −> db.limitTheNumberOfRecordsDemo.insertOne({"ClientName":"James Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9e601b50a6c6dd317adad") } > db.limitTheNumberOfRecordsDemo.insertOne({"ClientName":"Sam Williams"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9e60bb50a6c6dd317adae") } > db.limitTheNumberOfRecordsDemo.insertOne({"ClientName":"David Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9e612b50a6c6dd317adaf") } > db.limitTheNumberOfRecordsDemo.insertOne({"ClientName":"Carol Taylor"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9e61ab50a6c6dd317adb0") } > db.limitTheNumberOfRecordsDemo.insertOne({"ClientName":"Adam Smith"}); { "acknowledged" ...
Read MoreParticular field as result in MongoDB?
To get particular field as a result in MongoDB, you can use findOne(). Following is the syntax −db.yourCollectionName.findOne({"yourFieldName1":yourValue}, {yourFieldName2:1});Let us first create a collection with documents −> db.particularFieldDemo.insertOne({"EmployeeName":"John Smith", "EmployeeAge":26, "EmployeeTechnology":"MongoDB"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9b4abb50a6c6dd317ada2") } > db.particularFieldDemo.insertOne({"EmployeeName":"Chris Brown", "EmployeeAge":28, "EmployeeTechnology":"Java"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9b4d2b50a6c6dd317ada3") } > db.particularFieldDemo.insertOne({"EmployeeName":"David Miller", "EmployeeAge":30, "EmployeeTechnology":"MySQL"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9b4e8b50a6c6dd317ada4") } > db.particularFieldDemo.insertOne({"EmployeeName":"John Doe", "EmployeeAge":31, "EmployeeTechnology":"C++"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9b527b50a6c6dd317ada5") }Following is the query to display all documents from a collection with the help of ...
Read MoreMongoDB query where all array items are greater than a specified condition?
You can use $gt operator for this. Let us first create a collection with documents −> db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[89, 43, 32, 45]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9e9f9b50a6c6dd317adb3") } > db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[32, 33, 34, 40]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9ea13b50a6c6dd317adb4") } > db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[45, 56, 66, 69]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9ea25b50a6c6dd317adb5") } > db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[46, 66, 77, 88]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd9ea3cb50a6c6dd317adb6") }Following is the query to display all documents from a collection with the help of find() method −> db.arrayElementsNotGreaterThanDemo.find().pretty();This will produce the following output −{ ...
Read MoreHow to get array from a MongoDB collection?
You can use aggregate framework. Let us first create a collection with documents −> db.getArrayDemo.insertOne( { "CustomerId":101, "CustomerDetails":[ { "CustomerName":"Larry", "CustomerFriendDetails":[ { "CustomerFriendName":"Sam" }, { "CustomerFriendName":"Robert" } ...
Read MoreHow do I remove a string from an array in a MongoDB document?
You can use $pull operator to remove a string from an array. Let us first create a collection with documents −> db.removeAStringDemo.insertOne({"Score":[45, 67, 89, "John", 98, 99, 67]}); { "acknowledged" : true, "insertedId" : ObjectId("5cda5224b50a6c6dd317adbd") }Following is the query to display all documents from a collection with the help of find() method −> db.removeAStringDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cda5224b50a6c6dd317adbd"), "Score" : [ 45, 67, 89, "John", 98, 99, 67 ] ...
Read MoreFind a strict document that contains only a specific field with a fixed length?\\n
You can use $where operator for this. Let us first create a collection with documents −>db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Doe", "StudentAge":23}); { "acknowledged" : true, "insertedId" : ObjectId("5cda4bcdb50a6c6dd317adb8") } > db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"Larry"}); { "acknowledged" : true, "insertedId" : ObjectId("5cda4bdbb50a6c6dd317adb9") } >db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5cda4becb50a6c6dd317adba") } > db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5cda4bfbb50a6c6dd317adbb") } > db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"Bob", "StudentLastName":"Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5cda4c6db50a6c6dd317adbc") }Following is the query to display all documents from a collection with the help of find() method −> db.veryStrictDocumentDemo.find();This will produce the following output ...
Read MorePush new key element into subdocument of MongoDB?
You can use $set operator for this. Following is the syntax −db.yourCollectionName.update({"_id" : yourObjectId }, {$set: { "yourOuterFieldName.anyInnerFieldName": yourValue}});Let us first create a collection with documents −> db.pushNewKeyDemo.insertOne({"UserId":100, "UserDetails":{}}); { "acknowledged" : true, "insertedId" : ObjectId("5cda58f5b50a6c6dd317adbf") }Following is the query to display all documents from a collection with the help of find() method −> db.pushNewKeyDemo.find();This will produce the following output −{ "_id" : ObjectId("5cda58f5b50a6c6dd317adbf"), "UserId" : 100, "UserDetails" : { } }Following is the query to push new key element into subdocument of MongoDB −> db.pushNewKeyDemo.update({"_id" : ObjectId("5cda58f5b50a6c6dd317adbf")}, {$set: { "UserDetails.UserName": "David Miller"}}); WriteResult({ "nMatched" : 1, ...
Read MoreHow to push new items to an array inside of an object in MongoDB?
You can use $elemMatch operator for this. Let us first create a collection with documents −> db.pushNewItemsDemo.insertOne( { "_id" :1, "StudentScore" : 56, "StudentOtherDetails" : [ { "StudentName" : "John", "StudentFriendName" : [ "Bob", "Carol" ] }, { "StudentName" : ...
Read MoreHow to select where sum of fields is greater than a value in MongoDB?
You can use $where operator for this. Let us first create a collection with documents −> db.sumOfFieldIsGreaterThanDemo.insertOne({"Price1":10, "Price2":50, "Price3":40}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd84b8bf3115999ed511e6") } > db.sumOfFieldIsGreaterThanDemo.insertOne({"Price1":11, "Price2":1, "Price3":120}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd84c6bf3115999ed511e7") } > db.sumOfFieldIsGreaterThanDemo.insertOne({"Price1":10, "Price2":9, "Price3":6}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd84d2bf3115999ed511e8") }Following is the query to display all documents from a collection with the help of find() method −> db.sumOfFieldIsGreaterThanDemo.find();This will produce the following output −{ "_id" : ObjectId("5cdd84b8bf3115999ed511e6"), "Price1" : 10, "Price2" : 50, "Price3" : 40 } { "_id" : ObjectId("5cdd84c6bf3115999ed511e7"), "Price1" : ...
Read MoreEfficient way to remove all entries from MongoDB?
If you will try to use the method drop(), then it will delete all information about the collection. Indexing is fast. However, if you will use the method remove(), then it removes all records but keeps the collection and indexes.Let us check with the help of example.Using drop()Let us first create a collection with documents −> db.dropWorkingDemo.createIndex({"FirstName":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.dropWorkingDemo.insertOne({"FirstName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd8742bf3115999ed511e9") }Following is the query to display all documents from a collection with the ...
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