Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
You can use $match operator under aggregate() to get the first record. Let us first create a collection with documents −> db.conditionalFirstDemo.insertOne({_id:100, "StudentName":"Chris", "StudentSubject":null}); { "acknowledged" : true, "insertedId" : 100 } > db.conditionalFirstDemo.insertOne({_id:101, "StudentName":"Chris", "StudentSubject":null}); { "acknowledged" : true, "insertedId" : 101 } >db.conditionalFirstDemo.insertOne({_id:102, "StudentName":"Chris", "StudentSubject":"MongoDB"}); { "acknowledged" : true, "insertedId" : 102 } >db.conditionalFirstDemo.insertOne({_id:103, "StudentName":"Chris", "StudentSubject":"MongoDB"}); { "acknowledged" : true, "insertedId" : 103 } > db.conditionalFirstDemo.insertOne({_id:104, "StudentName":"Chris", "StudentSubject":null}); { "acknowledged" : true, "insertedId" : 104 }Following is the query to display all documents from a collection with the help of find() method −> db.conditionalFirstDemo.find();This will produce the following ... Read More
To prevent resizing columns, use the method setResizingAllowed(). Here, we will set setResizingAllowed() to false for table header to disallow resizing of columns from header −table.getTableHeader().setResizingAllowed(false);Let us first see an example wherein we can easily resize columns in a table by resizing the table column header −Examplepackage my; import java.awt.Color; import java.awt.Font; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.table.DefaultTableModel; public class SwingDemo { public static void main(String[] argv) throws Exception { DefaultTableModel tableModel = new DefaultTableModel(); JTable table = new JTable(tableModel); tableModel.addColumn("Language/ Technology"); tableModel.addColumn("Text Tutorial"); ... Read More
Consensus protocol is one of the most important aspects that makes the Block chain network a fool proof system. It is the revolutionary protocol that makes the Block chain network an irrefutable system where the majority of devices (nodes) connected to the network agree on each and every transaction. This prevents exploitation of the system as more than 51% consensus is required to create a new block. It is the core of the Block Chain which makes it certain that the information stored on the Block Chain is accurate and honest.The very core of the Nakamoto’s Block chain consensus protocol ... Read More
Let’s say you have saved the Login date of users. Now, you want the count of records for specific date only i.e. login date. For this, use $gte and $lt operator along with count(). Let us first create a collection with documents −> db.findDataByDateDemo.insertOne({"UserName":"John", "UserLoginDate":new ISODate("2019-01-31")}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd8cd7bf3115999ed511ed") } > db.findDataByDateDemo.insertOne({"UserName":"Larry", "UserLoginDate":new ISODate("2019-02-01")}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd8ce7bf3115999ed511ee") } > db.findDataByDateDemo.insertOne({"UserName":"Sam", "UserLoginDate":new ISODate("2019-05-02")}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd8cf3bf3115999ed511ef") } > db.findDataByDateDemo.insertOne({"UserName":"David", "UserLoginDate":new ISODate("2019-05-16")}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd8d00bf3115999ed511f0") } > db.findDataByDateDemo.insertOne({"UserName":"Carol", ... Read More
A Json array is an ordered collection of values that are enclosed in square brackets i.e. it begins with ‘[’ and ends with ‘]’. The values in the arrays are separated by ‘, ’ (comma).Sample JSON array{ "books": [ Java, JavaFX, Hbase, Cassandra, WebGL, JOGL] }The json-simple is a light weight library which is used to process JSON objects. Using this you can read or, write the contents of a JSON document using Java program.JSON-Simple maven dependencyFollowing is the maven dependency for the JSON-simple library − com.googlecode.json-simple json-simple ... Read More
In this section, we will see how to find the middle of three given values by comparing them. So if three numbers are given like (10, 30, 20), then it will find 20 as this is the middle element. Let us see the algorithm first, then we will implement that algorithm into C++ code.Algorithmmiddle_of_three(a, b, c): Input: Three numbers a, b and c Output: The middle of these three Begin if a > b, then if b > c, then return b else if a > c, then ... Read More
You can get the list of databases in MySQL using the SHOW DATABASES query.show databases;Following JDBC program retrieves the list of databases by executing the show databases query.Exampleimport java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class ShowDatabasesExample { public static void main(String args[]) throws Exception { //Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver()); //Getting the connection String mysqlUrl = "jdbc:mysql://localhost/mydatabase"; Connection con = DriverManager.getConnection(mysqlUrl, "root", "password"); System.out.println("Connection established......"); //Creating a Statement object Statement stmt = con.createStatement(); ... Read More
we can find the Maximum value of an array using Math.max() and sort() functions.1) Math.max()Math.max() function usually takes all the elements in an array and scrutinize each and every value to get the maximum value.It's methodology is discussed in the below example. Live DemoExample function maximum(value) { if (toString.call(value) !== "[object Array]") return false; return Math.max.apply(null, value); } document.write(maximum([6, 39, 55, 1, 44])); Output55.2) sort()Using sort and compare functions we can ... Read More
For this, use the $size operator. Let us first create a collection with documents −> db.checkIfListIsNotEmptyDemo.insertOne({"UserFriendGroup":["John", "David"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd99e8bf3115999ed511f7") } > db.checkIfListIsNotEmptyDemo.insertOne({"UserFriendGroup":["Carol"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd99e9bf3115999ed511f8") } > db.checkIfListIsNotEmptyDemo.insertOne({"UserFriendGroup":[]}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd99ebbf3115999ed511f9") } > db.checkIfListIsNotEmptyDemo.insertOne({"UserFriendGroup":[null]}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd99f2bf3115999ed511fa") } > db.checkIfListIsNotEmptyDemo.insertOne({"UserFriendGroup":[]}); { "acknowledged" : true, "insertedId" : ObjectId("5cdd99f6bf3115999ed511fb") }Following is the query to display all documents from a collection with the help of find() method −> db.checkIfListIsNotEmptyDemo.find().pretty();This will produce the following output −{ ... Read More
Here we will see what are the different types of C functions based on the return values and arguments.So a function either can take some arguments, or nothing is taken. Similarly, a function can return something, otherwise does not return anything. So we can categorize them into four types.Function with No argument and No return type.Function with No argument and Return something.A function that takes argument but returns nothing.Functions that take an argument and also return something.Example#include void my_function() { printf("This is a function that takes no argument, and returns nothing."); } main() { my_function(); }OutputThis is ... Read More