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Using WHERE Clause in JDBC

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Where clause is used to retrieve the data from a table based on some specific conditions.

Using WHERE Clause in JDBC

  

Where clause is used to retrieve the data from a table based on some specific conditions. It allows to filter the data from a table, a WHERE clause can be added to the SELECT statement. The WHERE clause searches the specific results by the SELECT statement.

Example of WHERE Clause

SELECT Name from Employee where Employee_ID=1;

Where clause Using LIKE

1.The following SQL statement will return employees with names that start with 'a':

SELECT * FROM Employee WHERE Name LIKE 'a%';

2.The following SQL statement will return employees with names that end with 'y':

SELECT * FROM Employee WHERE Name LIKE '%y';

3.The following SQL statement will return employees with names that contain the pattern 'as':

SELECT * FROM Employee WHERE Name LIKE '%as%';

A "%" and ??_?? sign is known as wildcards, both before and after the pattern.

Operators Used With WHERE Clause

= Equal

<> Not Equal

> Greater than

< Less than

>= Greater than or Equal

<= Less than or Equal

BETWEEN Between an inclusive range

LIKE Search for pattern

This program is concern with, how to get selected data from a table. Like- If any specific data desired then it would be easier as compare to search in whole table. So according to the Query the data would retrieve. In this program we used employee table which has Employee_ID field. So it will search in table and then give the result of an employee whose Employee_ID is 1. 

WhereClause.java

import java.sql.*;
public class WhereClause {
  public static void main(String a[])
  {
 Connection con = null;
 String url = "jdbc:mysql://localhost:3306/";
 String dbName = "vineej";
 String driver = "com.mysql.jdbc.Driver";
 String userName = "vineej";
 String password = "no";
 try {
  Class.forName(driver).newInstance();
  con = DriverManager.getConnection(url+dbName,userName,password);
  Statement st = con.createStatement();
   ResultSet rs = st.executeQuery("select Name from Employee where Employee_ID=1");  
  System.out.println("Results");
while( rs.next() ) { 
  String data = rs.getString(1); 
  System.out.println( data ); 
 } 
  st.close();
  }
  catch( Exception e ) {
  System.out.println(e.getMessage());
  e.printStackTrace();
 }
  }
} 


Description of program
This program making the connection between MySQL database and java with the help of many types of APIs interfaces. When it will be execute then it shows "Results" .The Employee is the table name and Employee_ID is the column name.

Description of code

1.Connection
An interface in java.sql package that provides connection with the database like- MySQL and java files. The SQL statements are executed within the context of the Connection interface.

2.Class.forName(String driver)
Class.forName method is static. This driver load the class and returns class instance and takes string type value and after that it will match the class with string.

3.DriverManager
It is a class of java.sql package that controls the JDBC drivers. Each driver has to be register with this class.

4.getConnection(String url, String userName, String password)
This method establishes a connection to specified database url. It takes three string types of arguments like:

url - Database url where stored or created your database
userName - User name of MySQL
password -Password of MySQL

5.con.close()
This method is used for disconnecting the connection. It frees all the resources occupied by the database.

6.printStackTrace()
The method is used to show error messages. If the connection is not connected then it throws the exception and print the message.

Download Source Code

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Posted on: June 27, 2008

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Comments
Java
December 8, 2011
updation

above statement will retrieve a particular details ("select Name from Employee where Employee_ID=1"); what need to be change in code which can accept and Employee_ID. Please Suggest.
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