In order to see the data from the table the most common type of SQL statement executed in most database environments is the query, or SELECT statement. Select statements retrieval requests data from tables in a database. You can issue a simple SELECT statement that is designed to retrieve all data from the table.
The SELECT statement is the most commonly used statement in SQL and is used to retrieve information already stored in the database. To retrieve data, you can either select all the column values or name specific columns in the SELECT clause to retrieve data.
Syntax of SELECT statement
SELECT [distinct] <tablename.columname >
FROM <tablename >
[where <condition>]
[group by <columnname(s)>]
[having <condition>]
[order by <expression>] ;
The Function Denote The Query ‘Selected Column’ This Will Fetch Record From Table With Selected Columns According To User Requirments.
First we have To Make a Table Named ‘Dept’ In MySql (Php MyAdmin) Into The DataBase Named ‘dbase’. Then We have to call The Packages From java Library.Then We Make a Class Named ‘JavaMySqlSelectedCol’ Extends “HttpServlet”. After Initializing The Class We Declare The Methods Public void Service()(The service method call the doGet() method for a GET request from User) and In That The Objects called “Response Object” and “Request Object Which will Work According To Work. After that We have to Load the Driver and Make Variables Of Resultset, Connection to establish The link between database and Query that Execute The Condition after Calling.After Declaring The Prepared statement We have to put the Query “SELECT dept_id, location_id FROM dept”.In that Query We Will fetch the record of (Dept_Id,Location_id) From the table Department. After that We will Use executeQuery() Method to Extract the Result On a Web Browser.
Now in the Other Hand If we Need to Show Output In tabular Form For Impressive view. We just use The Code of ‘HTML’ Into Java Code After Declaring all the Imp. Code Lines.. In The Last With the Using of Method DoGet() Produce the result on A web Browser..
Example :
JavaMySqlSelectedCol.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class JavaMySqlSelectedCol extends HttpServlet
{
public void service(HttpServletRequest rq, HttpServletResponse rp)throws IOException, ServletException
{
rp.setContentType("text/html");
PrintWriter disp = rp.getWriter();
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost/dbase";
String uid = "root";
String psw = "root";
Connection con=null;
PreparedStatement ps = null;
ResultSet rs;
try
{
Class.forName(driver);
con = DriverManager.getConnection(url,uid,psw);
ps=con.prepareStatement("SELECT dept_id, location_id FROM dept");
rs = ps.executeQuery();
String title = "Employee's Data With Selective Coloumns";
String docType ="<!doctype html public \"-//w3c//dtd html 4.0 " + "transitional//en\">\n";
disp.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f4efef\">\n" + "<h3 align=\"center\">" + title + "</h3>\n" + "<ul>\n" +
"<table width=\"50%\" border=\"1\" align=\"center\">\n" + "<th>Department Id</th><th>Location Id</th>\n"+ "</body> </html>");
while(rs.next())
{
String d_id = rs.getString("dept_id");
String l_id = rs.getString("location_id");
disp.println("<tr><td align=\"center\">"+ d_id +"<td align=\"center\">" + l_id +"</td></tr>" );
}
}
catch(Exception e)
{
e.printStackTrace();
}
disp.close();
}
public void doPost(HttpServletRequest rq,HttpServletResponse rp)throws IOException,ServletException
{
doGet(rq,rp);
}
}
web.xml
<servlet>
<servlet-name>JavaMySqlSelectedCol</servlet-name>
<servlet-class>JavaMySqlSelectedCol</servlet-class>
</servlet>
<!-- servlet mapping -->
<servlet-mapping>
<servlet-name>JavaMySqlSelectedCol</servlet-name>
<url-pattern>/JavaMySqlSelectedCol</url-pattern>
</servlet-mapping>
Dinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular