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You can select a single field in MongoDB using the following syntax:db.yourCollectionName.find({"yourFieldName":yourValue}, {"yourSingleFieldName":1, _id:0});In the above syntax "yourSingleFieldName":1, _id:0 means get all data from one field without _id.To understand the above syntax, let us create a collection with document. The query to create a collection with document is as follows:> db.singleFieldDemo.insertOne({"StudentName":"David", "StudentAge":28}); { "acknowledged" : true, "insertedId" : ObjectId("5c6eba356fd07954a489067c") } > db.singleFieldDemo.insertOne({"StudentName":"Bob", "StudentAge":18}); { "acknowledged" : true, "insertedId" : ObjectId("5c6eba406fd07954a489067d") } > db.singleFieldDemo.insertOne({"StudentName":"Chris", "StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5c6eba4c6fd07954a489067e") } > db.singleFieldDemo.insertOne({"StudentName":"Robert", "StudentAge":26}); { "acknowledged" : true, "insertedId" : ObjectId("5c6eba586fd07954a489067f") ... Read More
Most computer systems are single processor systems i.e., they only have one processor. However, multiprocessor or parallel systems are increasing in importance nowadays. These systems have multiple processors working in parallel that share the computer clock, memory, bus, peripheral devices etc. An image demonstrating the multiprocessor architecture is − Types of MultiprocessorsThere are mainly two types of multiprocessors i.e. symmetric and asymmetric multiprocessors. Details about them are as follows −Symmetric MultiprocessorsIn these types of systems, each processor contains a similar copy of the operating system and they all communicate with each other. All the processors are in a peer to ... Read More
Following are the different ways to handle exception messages in Java.Using printStackTrace() method − It print the name of the exception, description and complete stack trace including the line where exception occurred.catch(Exception e) { e.printStackTrace(); }Using toString() method − It prints the name and description of the exception.catch(Exception e) { System.out.println(e.toString()); }Using getMessage() method − Mostly used. It prints the description of the exception.catch(Exception e) { System.out.println(e.getMessage()); }Exampleimport java.io.Serializable; public class Tester implements Serializable, Cloneable { public static void main(String args[]) { try { int a = 0; ... Read More
In this tutorial, we will learn to check whether a value is a number in JavaScript. In JavaScript, it is necessary to check the variable's data type while performing some operation. Otherwise, it can create some unknown bugs in your application. For example, when users use the addition operator with the string, it concatenates the two strings, and in the same way, if users use the addition operator with a number, it adds two numbers. Now, think that the user wants to add two numbers but is concatenating the two strings. Here, we have three different methods to check whether ... Read More
Introduction Docker is a popular containerization platform that allows users to package and deploy applications in a standardized and isolated environment. Docker uses a file called a Dockerfile to specify the instructions for building and running a Docker container. One important element of a Dockerfile is the VOLUME instruction, which specifies a mount point for a volume in the container. In this article, we will explore the purpose and usage of volumes in a Dockerfile. Definition of volume in Dockerfile In the context of Docker, a volume is a persistent storage location that exists outside of the container. Volumes ... Read More
The services provided by the transport layer are explained below −Address MappingIt means mapping of transport address onto the network address. Whenever a session entity requests to send a transport service data unit (TSDU) to another session entity, it sends its transport service access point address as its identification. The transport entity then determines the network service access point (NSAP) address. This is known as address mapping.Assignment of Network ConnectionThe transport entity assigns a network connection for carrying the transport protocol data units (TPDUs). The transport entity establishes this assigned network connection. In some of the transport protocols, recovery from ... Read More
We can join two or more tensors using torch.cat(), and torch.stack(). torch.cat() is used to concatenate two or more tensors, whereas torch.stack() is used to stack the tensors. We can join the tensors in different dimensions such as 0 dimension, -1 dimension.Both torch.cat() and torch.stack() are used to join the tensors. So, what is the basic difference between these two methods?torch.cat() concatenates a sequence of tensors along an existing dimension, hence not changing the dimension of the tensors.torch.stack() stacks the tensors along a new dimension, as a result, it increases the dimension.StepsImport the required library. In all the following examples, ... Read More
First, we can define our dictionary and then, convert that dictionary into keys and values. Finally, we can use the data to plot a bar chart.StepsCreate a dictionary, i.e., data, where milk and water are the keys.Get the list of keys of the dictionary.Get the list of values of the dictionary.Plot the bar using plt.bar().Using plt.show(), show the figure.Exampleimport matplotlib.pyplot as plt data = {'milk': 60, 'water': 10} names = list(data.keys()) values = list(data.values()) plt.bar(range(len(data)), values, tick_label=names) plt.show()Output
This error comes whenever we add a foreign key constraint between tables and insert records into the child table. Let us see an example. Creating the child table. mysql> create table ChildDemo -> ( -> id int, -> FKPK int -> ); Query OK, 0 rows affected (0.86 sec) Creating the second table. mysql> create table ParentDemo -> ( -> FKPK int, -> Name varchar(100) -> , -> primary key(FKPK) ... Read More
This is a C++ program to read file line by line.Inputtpoint.txt is having initial content as "Tutorials point."OutputTutorials point.AlgorithmBegin Create an object newfile against the class fstream. Call open() method to open a file “tpoint.txt” to perform write operation using object newfile. If file is open then Input a string “Tutorials point" in the tpoint.txt file. Close the file object newfile using close() method. Call open() method to open a file “tpoint.txt” to perform read operation using object newfile. If file is open then Declare a ... Read More