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To drop a MongoDB database from the command line, use the following syntax:mongo yourDatabaseName --eval "db.dropDatabase()"To understand the above syntax, let us display all the database from MongoDB. The query is as follows −> show dbs;The following is the output −StudentTracker 0.000GB admin 0.000GB config 0.000GB local 0.000GB sample 0.000GB test 0.003GBDrop the database with the name ‘StudentTracker’. The query is as follows to drop a database from command line −C:\Program Files\MongoDB\Server\4.0\bin>mongo StudentTracker --eval "db.dropDatabase()"The following is the output −MongoDB shell version v4.0.5 connecting to: mongodb://127.0.0.1:27017/StudentTracker?gssapiServiceName=mongodb Implicit session: session { "id" : UUID("afc34e93-b4c0-46f0-85bd-b80ed17b8c11") } MongoDB server version: 4.0.5 { "dropped" ... Read More
The equivalent syntax is as follows.db.yourCollectionName.find({}, {_id: 1, "column1": 1, "column2": 1}).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"John", "CustomerAge":26, "CustomerCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6205259fcd19549980a") } > db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"David", "CustomerAge":22, "CustomerCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6305259fcd19549980b") } > db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"Chris", "CustomerAge":24, "CustomerCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6415259fcd19549980c") }Display all documents from a collection with the help of find() method. The query is as follows −> db.equivalentForSelectColumn1Column2Demo.find().pretty();The following is the output ... Read More
Python provides many ways to measure the time of execution for a piece of python code. One way is to use the python inbuilt time module and save the time before and after the execution of the program?Python timeitWhen some program is running, many processes also run in the background to make that code executable. The time module doesn’t count background processes execution time, however if you need precise time performance measurements timeit is the module to go for it.The timeit module runs the code approximately 1 million times (default value) and take into account the minimum amount of time ... Read More
This example demonstrate about How to use context in a fragmentStep 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. In the above code, we have taken two fragments.Step 3 − Add the following code to src/MainActivity.javapackage com.example.myapplication; import android.os.Bundle; import android.support.v4.app.FragmentActivity; public class MainActivity extends FragmentActivity { @Override public void onCreate(Bundle savedInstanceState) { ... Read More
Create an Instant and get an Instant using milliseconds passed as parameter from the epoch of 1970-01- 01T00:00:00Z. This is done using ofEpochMilli():Instant instant = Instant.ofEpochMilli(342627282920l);Now, get the Epoch milliseconds from Instant:instant. toEpochMilli();Exampleimport java.time.Instant; public class Demo { public static void main(String[] args) { Instant instant = Instant.ofEpochMilli(1262347200000l); long res = instant.toEpochMilli(); System.out.println(res); } }Output1262347200000
Yes, you can write own MySQL function to use in MySQL queries. Following is the syntax:DELIMITER // CREATE FUNCTION yourFunctionName(optional parameters)) RETURNS yourDataType DETERMINISTIC NO SQL BEGIN yourStatements1 . . . . N END // DELIMITER ;We have used the CREATE FUNCTION above to create a custom function.Let us create a custom MySQL function to use in MySQL query:mysql> DELIMITER // mysql> CREATE FUNCTION get_First_Name(Name VARCHAR(255)) RETURNS VARCHAR(255) DETERMINISTIC NO SQL BEGIN RETURN LEFT(Name, LOCATE(' ', Name) - 1); END // Query OK, 0 rows affected (0.20 sec) mysql> DELIMITER ;Now call ... Read More
The Central Processing Unit and the main memory are always very accurate and fast as compared with electromechanical input or output devices like printers, etc. Here in this case it is essential for us that the data lines of the computer are not engaged for a long time during communication process with input/output devices. Else the overall speed of the computer system drastically falls below. So the Input Output devices gets connected to a computer through the Input Output ports. Two Instructions are fetched which are called as IN and OUT where there are 256 Input Ports and 256 Output ... Read More
Let us see how to write a C program in which we can print the text “Hello World” without using any semicolon.We can simply write the text by using the line printf(“Hello World”); in the main() function.But there is a semicolon at the end of the line. To avoid the semicolon, we can follow some trick. We can use the same printf() statement inside if condition. As the printf() statement returns the length of the text, so it is non zero value, so the if statement will be true. Thus the text will be written on screen.Example Code#include main() { ... Read More
The session attribute indicates whether or not the JSP page uses HTTP sessions. A value of true means that the JSP page has access to a builtin session object and a value of false means that the JSP page cannot access the builtin session object.Following directive allows the JSP page to use any of the builtin object session methods such as session.getCreationTime() or session.getLastAccessTime() −
A RowId is a built-in type of SQL which is an address of a row in a table of a database. The RowId interface of the java.sql package maps with the SQL ROWID value.RowId values are unique for every row and they are the fastest way to access a row. You cannot use this as a primary key of a table.Retrieving RowId objectsYou can retrieve the RowId of a particular row using the getRowId() method of the ResultSet, CallableStatement, PreparedStatement interfaces.This method accepts a String value representing a column label or, an integer value representing the column index and returns ... Read More