executeQuery() Java Guide

In Java, the executeQuery() method is used to execute a query statement and return a result set. This method is typically used for executing SELECT statements.

Here are the general steps to use the executeQuery() method:

1. Create a Connection object to connect to the database.
2. Create a Statement object for executing SQL statements.
3. Execute a query statement using the executeQuery() method of the Statement object, and store the returned ResultSet object in a variable.
4. Iterate through the ResultSet object to retrieve the query results.

The following is an example code demonstrating how to use the executeQuery() method to retrieve data from a database.

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        try {
            // 创建一个Connection对象
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");

            // 创建一个Statement对象
            Statement stmt = conn.createStatement();

            // 执行查询语句并获取结果集
            ResultSet rs = stmt.executeQuery("SELECT * FROM mytable");

            // 遍历结果集并输出数据
            while (rs.next()) {
                System.out.println(rs.getString("column1") + " " + rs.getString("column2"));
            }

            // 关闭连接
            rs.close();
            stmt.close();
            conn.close();

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

In the example above, we start by creating a Connection object, followed by creating a Statement object. Next, we execute a SELECT statement using the executeQuery() method and store the results in a ResultSet object. Finally, we loop through the ResultSet object and display the query results. Lastly, we close the ResultSet, Statement, and Connection objects.