Retrieve data example

This is an example of how to retrieve data from a database. Retrieving data from a database implies that you should:

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class SelectRowsExample {
 
  public static void main(String[] args) {
    Connection connection = null;
    try {
  // Load the MySQL JDBC driver
  String driverName = "com.mysql.jdbc.Driver";
  Class.forName(driverName);
  // Create a connection to the database
  String serverName = "localhost";
  String schema = "test";
  String url = "jdbc:mysql://" + serverName +  "/" + schema;
  String username = "username";
  String password = "password";
  connection = DriverManager.getConnection(url, username, password);
  
  System.out.println("Successfully Connected to the database!");
  
    } catch (ClassNotFoundException e) {
  System.out.println("Could not find the database driver " + e.getMessage());
    } catch (SQLException e) {
  System.out.println("Could not connect to the database " + e.getMessage());
    }
    try {
// Get a result set containing all data from test_table
Statement statement = connection.createStatement();
ResultSet results = statement.executeQuery("SELECT * FROM test_table");
// For each row of the result set ...
while (results.next()) {
  // Get the data from the current row using the column index - column data are in the VARCHAR format
  String data = results.getString(1);
  System.out.println("Fetching data by column index for row " + results.getRow() + " : " + data);
  // Get the data from the current row using the column name - column data are in the VARCHAR format
  data = results.getString("test_col");
  System.out.println("Fetching data by column name for row " + results.getRow() + " : " + data);
}
/*
  * Please note :
  * ResultSet API provides appropriate methods for retrieving data 
  * based on each column data type e.g.
  * 
  * boolean bool = rs.getBoolean("test_col");
  * byte b = rs.getByte("test_col");
  * short s = rs.getShort("test_col");
  * int i = rs.getInt("test_col");
  * long l = rs.getLong("test_col");
  * float f = rs.getFloat("test_col");
  * double d = rs.getDouble("test_col");
  * BigDecimal bd = rs.getBigDecimal("test_col");
  * String str = rs.getString("test_col");
  * Date date = rs.getDate("test_col");
  * Time t = rs.getTime("test_col");
  * Timestamp ts = rs.getTimestamp("test_col");
  * InputStream ais = rs.getAsciiStream("test_col");
  * InputStream bis = rs.getBinaryStream("test_col");
  * Blob blob = rs.getBlob("test_col");
  */
    } catch (SQLException e) {
  System.out.println("Could not retrieve data from the database " + e.getMessage());
    }
  }
}

Example Output:

Successfully Connected to the database!
Fetching data by column index for row 1 : new_test_value
Fetching data by column name for row 1 : new_test_value
Fetching data by column index for row 2 : new_test_value_0
Fetching data by column name for row 2 : new_test_value_0
Fetching data by column index for row 3 : new_test_value_1
Fetching data by column name for row 3 : new_test_value_1
Fetching data by column index for row 4 : new_test_value_2
Fetching data by column name for row 4 : new_test_value_2
Fetching data by column index for row 5 : new_test_value_3
Fetching data by column name for row 5 : new_test_value_3
Fetching data by column index for row 6 : new_test_value_4
Fetching data by column name for row 6 : new_test_value_4
Fetching data by column index for row 7 : new_test_value_5
Fetching data by column name for row 7 : new_test_value_5
Fetching data by column index for row 8 : new_test_value_6
Fetching data by column name for row 8 : new_test_value_6
Fetching data by column index for row 9 : new_test_value_7
Fetching data by column name for row 9 : new_test_value_7
Fetching data by column index for row 10 : new_test_value_8
Fetching data by column name for row 10 : new_test_value_8
Fetching data by column index for row 11 : new_test_value_9
Fetching data by column name for row 11 : new_test_value_9

 
This was an example of how to retrieve data from a database in Java.

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