How to add a column in a table
Consider a situation where the requirement of the
client gets changed and you have asked to modify the structure of the table. In
reality it is the work of the database administrator but as a Java programmer
you should know how you can modify the structure of the table. The problem is
that we have to add a new column to our database by using the java program.
There is no need to get panic. What we simply need is to use a query for
adding a new column in the database table.
To get the desired result firstly we need to make a
connection with our database. After connection has been established pass the
query in the prepareStatement() for adding new column in the database.
This method will return the PreparedStatement object. By the object of
the PreparedStatement we will call the executeUpdate() which will
tell the status of the table.
The code of the example is given below:
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ServletAddingNewColumn extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException{
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
String connectionURL = "jdbc:mysql://localhost/zulfiqar";
Connection connection;
try{
Class.forName("org.gjt.mm.mysql.Driver");
connection = DriverManager.getConnection(connectionURL, "root", "admin");
PreparedStatement pst = connection.prepareStatement
("alter table emp_details add column sal int(5)");
int i = pst.executeUpdate();
if (i==1){
pw.println("Column has been added");
}
else{
pw.println("No column has been added");
}
}
catch(Exception e){
pw.println("The exception is " + e);
}
}
}
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web.xml file for this program:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<servlet>
<servlet-name>Zulfiqar</servlet-name>
<servlet-class>ServletAddingNewColumn</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Zulfiqar</servlet-name>
<url-pattern>/ServletAddingNewColumn</url-pattern>
</servlet-mapping>
</web-app>
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The output of the program is given below:
Download this
example
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