java使用教程如何使用JDBC执行SQL语句 java使用教程的数据库操作技巧​

finally

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class JdbcQueryExample {

    // 假设你的数据库连接信息
    private static final String DB_URL = "jdbc:mysql://localhost:3306/testdb?useSSL=false&serverTimezone=UTC";
    private static final String USER = "root";
    private static final String PASS = "your_password";

    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            // 1. 加载JDBC驱动 (对于新版本JDBC驱动，通常可以省略这步，但写上无妨)
            // Class.forName("com.mysql.cj.jdbc.Driver"); // MySQL 8.0+

            // 2. 建立连接
            conn = DriverManager.getConnection(DB_URL, USER, PASS);
            System.out.println("数据库连接成功！");

            // 3. 准备SQL语句 (使用PreparedStatement，防止SQL注入)
            String sql = "SELECT id, name, age FROM users WHERE age > ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, 25); // 设置参数，第一个问号对应25

            // 4. 执行查询
            rs = pstmt.executeQuery();

            // 5. 处理查询结果
            System.out.println("查询结果：");
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                System.out.println("ID: " + id + ", 姓名: " + name + ", 年龄: " + age);
            }

        } catch (SQLException e) {
            // 捕获并处理SQL异常
            System.err.println("数据库操作异常：" + e.getMessage());
            e.printStackTrace();
        } finally {
            // 6. 关闭资源，确保连接被释放
            try {
                if (rs != null) rs.close();
                if (pstmt != null) pstmt.close();
                if (conn != null) conn.close();
                System.out.println("资源已关闭。");
            } catch (SQLException e) {
                System.err.println("关闭资源时发生异常：" + e.getMessage());
            }
        }
    }
}

Statement

"SELECT * FROM users WHERE id = 100"

"SELECT * FROM users WHERE id = 200"

PreparedStatement

?

"SELECT * FROM users WHERE id = ?"

setXxx()

PreparedStatement

Statement

CREATE TABLE

DROP TABLE

PreparedStatement

PreparedStatement