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In order to delete the collection which has some special characters like _ or -, you need to use the following syntax −db.getCollection("yourCollectionName").drop();To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.createCollection("_personalInformation"); { "ok" : 1 } > db.getCollection('_personalInformation').insertOne({"ClientName":"Chris", "ClientCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9158bb4afe5c1d2279d6b2") } > db.getCollection('_personalInformation').insertOne({"ClientName":"Mike", "ClientCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9158c84afe5c1d2279d6b3") } > db.getCollection('_personalInformation').insertOne({"ClientName":"David", "ClientCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9158d54afe5c1d2279d6b4") }Display all documents from a collection with the ... Read More
You can get the number of columns of a table using the getColumnCount() method of the ResultSetMetaData class.//Retrieving the ResultSetMetaData object ResultSetMetaData rsmd = rs.getMetaData(); //getting the column type int column_count = rsmd.getColumnCount();Assume we have a table named employee_data in the database with description as shown below:+----------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | Name | varchar(255) | YES | ... Read More
In this section we are going to develop a command line interface using python. But before we deep dive into program, lets first understand command line.Command line are in use since the existence of computer programs and are built on commands. A command line program is a program that runs from a shell or from a command lineWhile command line interface provides user interface that is navigated by typing commands at terminals, shells or consoles instead of using the mouse.A command-line interface(CLI) starts with an executable. There are parameters which we can pass to the script depending how they are ... Read More
In order to return only value of a field in MongoDB, you need to write a query and use forEach loop. Let us first create a collection with documents> db.returnOnlyValueOfFieldDemo.insertOne({"ClientName":"Larry"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9ea537d628fa4220163b6e") } > db.returnOnlyValueOfFieldDemo.insertOne({"ClientName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9ea53bd628fa4220163b6f") } > db.returnOnlyValueOfFieldDemo.insertOne({"ClientName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9ea541d628fa4220163b70") } > db.returnOnlyValueOfFieldDemo.insertOne({"ClientName":"Ramit"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9ea549d628fa4220163b71") }Following is the query to display all documents from a collection with the help of find() method> db.returnOnlyValueOfFieldDemo.find().pretty();This will produce the following output{ "_id" : ... Read More
To check capacity in Java, firstly create a list and add elements. After that use ensureCapacity() and increase the capacity.Let us first create an ArrayList and add some elements −ArrayListarrList = new ArrayList(5); arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500);Now, increase the capacity of the ArrayList −arrList.ensureCapacity(15);Meanwhile, with the size() method, you can check the current size of the ArrayList as well.Example Live Demoimport java.util.ArrayList; public class Demo { public static void main(String[] a) { ArrayListarrList = new ArrayList(5); arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500); ... Read More
Yes, you can use SUM() with IF() in MySQL. Let us first create a demo table:mysql> create table DemoTable ( Value int, Value2 int ); Query OK, 0 rows affected (0.51 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable values(100, 400); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(100, 400); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(400, 100); Query OK, 1 row affected (0.14 sec)Following is the query to display records from the table using select command:mysql> select *from DemoTable;This ... Read More
The method java.io.File.renameTo() is used to rename a file or directory. This method requires a single parameter i.e. the name that the file or directory is renamed to and it returns true on the success of the renaming or false otherwise.A program that demonstrates this is given as follows −Example Live Demoimport java.io.File; public class Demo { public static void main(String[] args) { try { File file1 = new File("demo1.txt"); File file2 = new File("demo2.txt"); file1.createNewFile(); file2.createNewFile(); ... Read More
In this program we will see how to add two 16-bit numbers with and without carry.Problem StatementWrite 8086 Assembly language program to add two 16-bit number stored in memory location 3000H – 3001H and 3002H – 3003H.Discussion8086 is 16-bit register. We can simply take the numbers from memory to AX and BX register, then add them using ADD instruction. When the Carry is present store carry into memory, otherwise only store AX into memory.We are taking two numbers BCAD + FE2D = 1BADAInput:AddressData……3000AD3001BC30022D3003FE…… Flow Diagram ProgramOutputAddressData……3004DA3005BA300601……
In C++ when we want to create a new object, we have to create a memory block into the memory, then also call constructor to initialize the memory block. We can create memory element by using the new keyword. This new operator is doing two consecutive task. But the operator new just only create memory space.New KeywordThe new operator is a special type of operator, which denotes a request for memory allocation on the heap section. When sufficient memory is available, then only new operators initializes the memory to the pointer variable. When we create an object using a normal ... Read More
The session object is used to track a client session between client requests.JSP makes use of the servlet provided HttpSession Interface. This interface provides a way to identify a user across.a one-page request orvisit to a website orstore information about that userBy default, JSPs have session tracking enabled and a new HttpSession object is instantiated for each new client automatically. Disabling session tracking requires explicitly turning it off by setting the page directive session attribute to false as follows −The JSP engine exposes the HttpSession object to the JSP author through the implicit session object. Since the session object is ... Read More