java sql query code example

Example 1: how to write queries in java

import java.sql.*;

/**
 * A Java MySQL SELECT statement example.
 * Demonstrates the use of a SQL SELECT statement against a
 * MySQL database, called from a Java program.
 * 
 * Created by Alvin Alexander, http://alvinalexander.com
 */
public class JavaMysqlSelectExample
{

  public static void main(String[] args)
  {
    try
    {
      // create our mysql database connection
      String myDriver = "org.gjt.mm.mysql.Driver";
      String myUrl = "jdbc:mysql://localhost/test";
      Class.forName(myDriver);
      Connection conn = DriverManager.getConnection(myUrl, "root", "");
      
      // our SQL SELECT query. 
      // if you only need a few columns, specify them by name instead of using "*"
      String query = "SELECT * FROM users";

      // create the java statement
      Statement st = conn.createStatement();
      
      // execute the query, and get a java resultset
      ResultSet rs = st.executeQuery(query);
      
      // iterate through the java resultset
      while (rs.next())
      {
        int id = rs.getInt("id");
        String firstName = rs.getString("first_name");
        String lastName = rs.getString("last_name");
        Date dateCreated = rs.getDate("date_created");
        boolean isAdmin = rs.getBoolean("is_admin");
        int numPoints = rs.getInt("num_points");
        
        // print the results
        System.out.format("%s, %s, %s, %s, %s, %s\n", id, firstName, lastName, dateCreated, isAdmin, numPoints);
      }
      st.close();
    }
    catch (Exception e)
    {
      System.err.println("Got an exception! ");
      System.err.println(e.getMessage());
    }
  }
}

Example 2: sql query in java

stmt = con.createStatement();

Example 3: create statement in jdbc

Connection = 
  Helps our java project connect to database
Statement = 
  Helps to write and execute SQL query
ResultSet = 
  A DataStructure where the data from query result stored
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    

  After succesfully created the connect
next step is STATEMENT

Statement statement = connection.createStatement();
We use createStatement() method to create
the statement from our connection.
-The result we get from this type of statement
can only move from top to bottom,
not other way around

Statement statement = connection.
createStatement(ResultSet TYPE_SCROLL_INSENSITIVE
,ResultSet CONCUR_READ_ONLY);

-The result we get from this type of
statement can freely move between rows

Once we have statement we can run
the query and get the result to
ResultSet format 
		import java.sql.ResultSet;
        
We use the method executeQuery()
to execute our queries

ResultSet result = statement.
              executeQuery("Select * from employees");

Example 4: how to write queries in java

2, Fred, Flinstone, 2010-06-23, false, 6000
3, Barney, Rubble, 2010-06-23, false, 5000

Example 5: sql query in java

ResultSet rs = stmt.executeQuery(query);